[llvm] [AMDGPU][NFC] Added Pre-commit tests for PR#137137 (PR #137150)

[Vikash Gupta via llvm-commits]

vg0204 wrote:

> No, if there are missing type cases in the existing tests they can be added there. As it is this looks wholly redundant

Here, the main differentiation should be vectors of fp16 (having different element numbers), in order to see how packing is handled in different scenarios. As for missing, we could compare the changes observed in existing cases by #137137 to identify ones those are missing & let it be here, I guess!

https://github.com/llvm/llvm-project/pull/137150