[Headers][X86] Allow AVX512F mullox intrinsics to be used in constexpr

[RKSimon]

Forgot to include these in #155411

_mm512_mullox_epi64 
_mm512_mask_mullox_epi64 

[llvmbot]

Hi!

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[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: Simon Pilgrim (RKSimon)

Forgot to include these in #155411 ``` _mm512_mullox_epi64 _mm512_mask_mullox_epi64 ```

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Simon Pilgrim (RKSimon)

Forgot to include these in #155411 ``` _mm512_mullox_epi64 _mm512_mask_mullox_epi64 ```