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

[Shilei Tian via llvm-commits]

shiltian 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 work? I tried locally and the assembler can still recognize it.

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