[llvm] [AMDGPU][True16][CodeGen] update isel pattern with vgpr16 for 16 bit types (PR #154875)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> CI error not related

The CI shows these two tests being broken:
```
  LLVM :: CodeGen/AMDGPU/fcopysign.gfx11plus.ll
  LLVM :: CodeGen/AMDGPU/scalar_to_vector.gfx11plus.ll
```

Those tests were added in this PR? How are the failures not related?

This change also broke postcommit buildbots. Please either revert or fix forward.

https://github.com/llvm/llvm-project/pull/154875