[Codegen][X86] Fix /HOTPATCH with clang-cl and inline asm (#87639)

This fixes an edge case where functions starting with inline assembly
would assert while trying to lower that inline asm instruction.

After this PR, for now we always add a no-op (xchgw in this case) without
considering the size of the next inline asm instruction. We might want
to revisit this in the future.

This fixes Unreal Engine 5.3.2 compilation with clang-cl and /HOTPATCH.

Should close https://github.com/llvm/llvm-project/issues/56234

(cherry picked from commit ec1af63d)