[llvm] [AMDGPU] Add test to show failure with SRC_*_HI registers. NFC. (PR #154828)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

Then basically given low32 are useless and hi32 are inaccessible, I wish it all had been done differently. But that train has sailed by zeppelin long time ago. We may want to explore a way to produce a pseudo reading just these registers and do not include it in any of the SReg* classes. It might be easier.

https://github.com/llvm/llvm-project/pull/154828