[llvm] AMDGPU: Add sgpr bit convert tests (PR #136112)

[Matt Arsenault via llvm-commits]

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+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
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arsenm wrote:

Test filenames still mention inreg this is not about inreg. This is the scalar case, and these can merge with the existing type size tests 

https://github.com/llvm/llvm-project/pull/136112