[llvm] [AMDGPU][MC] Use normal ELF syntax for section switching (PR #77267)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > Does the assembler still recognize the sun syntax? Can you add a test for what happens if you try reading old asm with the sun name?
> 
> Do we still want the sun style to work? I tried locally and the assembler can still recognize it.

Well we ideally wouldn't break existing asm people are relying on parsing 

https://github.com/llvm/llvm-project/pull/77267