[llvm] [AMDGPU][GlobalISel] Update tests to check for COV5 (PR #76257)

[Changpeng Fang via llvm-commits]

changpeng wrote:

Ideally we prefer the LIT tests not to specify module flag of code object version. The exceptions are to check the features related to particular code object version. This is to say for the tests to check unrelated issues (unrelated to particular cov), it is better just to keep just one copy of the test with default code object version. 
When you specify cov5, it essentially stops a test for future code object version. 
Would you please double check whether these tests are for the feature of cov5 only? (not useful/valid for other covs), Thanks.

https://github.com/llvm/llvm-project/pull/76257