[llvm] [AMDGPU][True16][MC] Support v_swap_b16. (PR #100442)

[Joe Nash via llvm-commits]

Sisyph wrote:

Can you please commit a separate patch first that contains the changes to llvm/test/MC/AMDGPU/gfx12_asm_vop1-fake16.s and llvm/test/MC/AMDGPU/gfx12_asm_vop1.s minus v_swap_b16? The files look fine, just adding that bulk test update should be separate from the functional change to v_swap_b16. 

https://github.com/llvm/llvm-project/pull/100442