hardcode defs_div_sqrt_mvp pkg into gen_sources.sh for fpnew synthesis

[JulessD]

The package defs_div_sqrt_mvp of the fpnew was not recognized as a package in hw/scripts/gen_sources.sh script because the filename does not contain the substring "_pkg", resulting in it not being put at the top of the generated flist and resulting in a compilation error.
Proposed fix: Hardcode the defs_div_sqrt_mvp package name into gen_sources script.
No functional change.

The problem was found when using the script to generate a filelist for Questasim.

[tinebp]

Problem confirmed — reproduced exactly as you described (defs_div_sqrt_mvp.sv listed
after control_mvp.sv, which imports it). We landed a different implementation as
d4205f5, credited to your report: classifying flist entries by content (a leading
'package' declaration) rather than filename. Two reasons we didn't take the hardcode:
it names one third-party file in three places (the next nonconforming vendored package
regresses again), and the catch-all finds were not updated to exclude it, so the file
was emitted twice in every mode. The content-based version hoists it first and exactly
once, and produces byte-identical filelists to the old script on all existing flows.
Thanks for exercising the Questa path — both of your reports were real.