belt-dwp: migrate to the `ghash` crate

[newpavlov]

belt-dwp currently uses a vendored version of the ghash code with small tweaks required by the specification. We probably should tweak ghash accordingly and migrate belt-dwp to it.

[makavity]

Looks like we should add Le an Be operations, right?

[newpavlov]

I don't remember. I will need to take a look at the belt-dwp spec and compare it against implementation in ghash.

[makavity]

Additional functionality in belt-dwp is only xor_s. If it is ok to add this function in GHash crate and add le or be flavor - can commit it.

[newpavlov]

Could you open two PRs for ghash and for belt-dwp with migration to it? You can use the dependency patching for the second PR.

[makavity]

Yeah, sure.

[makavity]

xor_s is useless. It is replaced with just update_padded.
But now I have some problems with little endian/big endian.
Should I add flavors for arithmetic in the polyval crate?

[newpavlov]

Should I add flavors for arithmetic in the polyval crate?

Yeah, it's probably has to be done.