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

For some reasons `SunStyleELFSectionSwitchSyntax` is set to `true` for
AMDGPU, but according to
https://github.com/llvm/llvm-project/issues/64862#issuecomment-1880419239
that syntax is only limited to Sun system.

Fix #64862.