[llvm] [AMDGPU] Get rid of the +wavefrontsizeXX,-wavefrontsizeXX in MC tests (PR #99001)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> > Now turning off/turning on feature is not needed in most cases. This is NFC, tests only.
> 
> What is the behavior now? Specifying either of +wavefrontsize32 or +wavefrontsize64 automatically turns off the other one? But there is still a default if you specify neither, right?

There is default, it is wave32 if wave32 is supported. If you specify +wavefrontsize64 it will turn off wave32 automatically.

https://github.com/llvm/llvm-project/pull/99001