[llvm] [AMDGPU][True16] fix a bug in codeGen causing e64 with wrong vgpr type to shrink (PR #102942)

[Joe Nash via llvm-commits]

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

LGTM. We can revert this part of the patch until all instructions are properly updated.

https://github.com/llvm/llvm-project/pull/102942