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

[Fangrui Song via llvm-commits]

MaskRay wrote:

Agreed that `TextAlignFillValue = 0` can be removed as x86 has the only use (and downstream targets tend to be RISC and unlikely need such mechanism).

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