[llvm] [X86] Don't request 0x90 nop filling in p2align directives (PR #110134)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay approved this pull request.

LGTM.

Is there any test that uses `.p2align 4{{$}}` so that it will catch `.p2 align 4, 0x90` regression?

https://github.com/llvm/llvm-project/pull/110134