Review proposed PQC kernel support

[mimizohar]

David Howells and Eric Biggers proposed PQC ML-DSA pure mode support, but does not support IMA [1].

Summary:

• The ML-DSA implementation supports only "pure" mode, not pre-hash mode.

By not supporting "pre-hash" mode, IMA file hash will be calculated multiple times, once by the kernel for audit and extending the TPM, and again by the ML-DSA crypto. Review the proposed ML-DSA code to see if this is even possible and how hard it would be.

[1] Link: https://lore.kernel.org/linux-integrity/1783975.1769190197@warthog.procyon.org.uk/

[mimizohar]

David Howell's and Eric Bigger's cML-DSA code was upstreamed in the 7.0 open window. Instead of adding "pre-hash" mode, Eric Biggers suggested signing the "ima_file_id" structure, which contains the hash. Only fsverity signatures(v3) use the "ima_file_id" structure. Add similar kernel support for regular file data hash based signatures.