ppc64le: Added optimized ppc64le support functions for ML-KEM.

[dannytsen]

Added optimized ppc64le support functions for ML-KEM.

Supported native functions are:

1. MLK_USE_NATIVE_NTT (ntt_ppc.S)
2. MLK_USE_NATIVE_INTT (intt_ppc.S)
3. MLK_USE_NATIVE_POLY_REDUCE (reduce.S)
4. MLK_USE_NATIVE_POLY_TOMONT (poly_tomont.S)

Signed-off-by: Danny Tsen dtsen@us.ibm.com

• Does this PR change the input/output behaviour of a cryptographic algorithm (i.e., does it change known answer test values)? (If so, a version bump will be required from x.y.z to x.(y+1).0.)
• Does this PR change the list of algorithms available -- either adding, removing, or renaming? Does this PR otherwise change an API? (If so, PRs in fully supported downstream projects dependent on these, i.e., oqs-provider will also need to be ready for review and merge by the time this is merged.)

[dstebila]

Thanks for working on this!

Since we are pulling the mlkem-native implementation from the mlkem-native project, I think the preference would be for this code to be first added to mlkem-native, and then we will be able to pull it automatically into liboqs. This would benefit other users of mlkem-native as well as keep our integration process more automated. Would that be possible for you?

[dannytsen]

Thanks for working on this!

Since we are pulling the mlkem-native implementation from the mlkem-native project, I think the preference would be for this code to be first added to mlkem-native, and then we will be able to pull it automatically into liboqs. This would benefit other users of mlkem-native as well as keep our integration process more automated. Would that be possible for you?

@dstebila Sure. I can do that. Then, we can close this PR. Thanks.

[dannytsen]

Close this PR. Will use mlkem-native project.