arch/arm/src/imxrt: Unify FlexCAN TX work and add SIOCGCANERRORS.

[dakejahl]

Summary

Two changes to the i.MX RT FlexCAN SocketCAN driver, plus the network-layer plumbing the second one needs. Reworked per review: the per-command CAN ioctl options are merged into a single NETDEV_CAN_IOCTL.

1. NETDEV_CAN_BITRATE_IOCTL, NETDEV_CAN_FILTER_IOCTL and NETDEV_CAN_STATE_IOCTL guarded identical option blocks, and every SIOCxCANxxx case in netdev_ifr_ioctl() forwarded a member of the same ifr_ifru union to d_ioctl(). They are merged into one NETDEV_CAN_IOCTL option and one case block that passes the union's address; drivers and defconfigs are updated to the new name. The stm32h7 FDCAN filter cases called stm32_addextfilter(), stm32_delextfilter(), stm32_addstdfilter() and stm32_delstdfilter(), which exist nowhere in the tree and only ever compiled because no stm32h7 config enables NETDEV_CAN_FILTER_IOCTL; a preparatory commit removes them so the commands fall through to the existing -ENOTSUP default.
2. imxrt_txdone_work() and imxrt_txtimeout_work() shared priv->irqwork. work_queue() cancels a pending callback when its work_s is reused, so whichever was queued second silently replaced the first: deadlines left set, IMASK1 TX bits left off, or expired frames never aborted. Both paths now queue one worker, imxrt_tx_work(), which retires completions before aborting expired mailboxes.
3. A new SIOCGCANERRORS ioctl (_SIOC(0x0045), behind CONFIG_NETDEV_CAN_IOCTL) returns struct can_ioctl_errors_s: fault-confinement state, TEC, REC, a monotonic bus-error count and the RX mailbox overrun count. SIOCGCANSTATE reports sleep/operational, not fault confinement, so this is a distinct command. The driver counts bus errors by sampling the clear-on-read ESR1 error flags at every driver entry (TX work, RX work, the ioctl) instead of enabling ERRINT, which fires per error frame and storms at bus rate on a dead bus. Frames the CAN socket layer drops for want of an IOB now also count as rx_dropped in the per-device netdev statistics.

Impact

• New feature: YES, SIOCGCANERRORS, implemented for i.MX RT FlexCAN only; other SocketCAN drivers return -ENOTTY.
• User: YES. NETDEV_CAN_BITRATE_IOCTL, NETDEV_CAN_FILTER_IOCTL and NETDEV_CAN_STATE_IOCTL no longer exist; configs that enabled any of them must enable NETDEV_CAN_IOCTL instead (in-tree defconfigs are updated). A board that enabled only one command's option now compiles every CAN ioctl case its driver implements.
• Build: NO change with the option disabled; include/net/if.h gains struct can_ioctl_errors_s and one union member in ifreq/lifreq. The drivers touched by the rename get whole-file nxstyle fixes (whitespace only, token streams verified identical).
• Hardware: i.MX RT FlexCAN only (the TX worker change affects every i.MX RT SocketCAN user).
• Documentation: NO documentation of the CAN ioctls exists to update.
• Security: NO.
• Compatibility: YES for the ioctl (backward compatible; ifreq does not grow). NO for the three removed config names, see User above.

Testing

Build: imxrt1170-evk:can with CONFIG_NETDEV_CAN_IOCTL=y, nucleo-h743zi2:socketcan, imx95-evk:can, sim:dynconns, arm-none-eabi-gcc 13.2.1, host Linux.

Runtime: i.MX RT1176 (ARK FMU-v6XRT) running PX4 with this change carried on the PX4 NuttX fork (PX4/NuttX#401), two DroneCAN nodes, one per FlexCAN interface, 1 Mbit/s.

Before (stub getErrorCount(), isInBusOffState()): an error-passive controller is invisible from the socket API; uavcan status prints HW errors: 0 regardless.

After, unplugging the CAN2 node for 10 s and reading the ioctl every 2 s (console) while ECR/ESR1 were read over SWD at 20 Hz:

 64.1s  CAN1 error-active TEC 0 REC 0 hw 0    |  CAN2 error-passive TEC 128 REC 0 hw 379
 66.8s  CAN1 error-active TEC 0 REC 0 hw 0    |  CAN2 error-passive TEC 128 REC 0 hw 451
 74.7s  CAN1 error-active TEC 0 REC 0 hw 0    |  CAN2 error-passive TEC 128 REC 0 hw 637
 77.4s  CAN1 error-active TEC 0 REC 0 hw 0    |  CAN2 error-passive TEC 152 REC 0 hw 659
 85.3s  CAN1 error-active TEC 0 REC 0 hw 0    |  CAN2 error-active  TEC 17  REC 0 hw 660
SWD: CAN2 TXERRCNT 128 from 66.9 s, ESR1 fault confinement error-passive, 302 samples over 23 s, 259 with ACKERR; CAN1 0 / error-active on all 5932 samples

With the two nodes moved to 500 kbit/s while the controller stayed at 1 Mbit/s, the ioctl reads error-passive (TEC 0, REC 128) while the controller transmits nothing and (TEC 128, REC 133) while it does. With NETDEV_STATISTICS enabled, /proc/net/can0 showed Dropped advancing (445 frames in 300 s at 3260 frames/s with a 24-buffer IOB pool), which the global CAN statistics alone did not attribute to an interface.

[github-actions]

MemBrowse Memory Report

No memory changes detected for:

• arduino-mega2560
• esp32-devkitc
• hifive1-revb
• mirtoo
• qemu-armv8a
• qemu-intel64
• rx65n-rsk2mb
• s698pm-dkit
• stm32-nucleo-f103rb