[llvm] [AMDGPU] Change the immediate operand of s_waitcnt_depctr / s_wait_alu (PR #169378)

[Carl Ritson via llvm-commits]

https://github.com/perlfu commented:

Is there any way you can keep the undefined/reserved bits in the mask as 1?
While it's probably fine if they are 0 they have always been set, so we need to double check there aren't any unintended consequences of not setting them.

https://github.com/llvm/llvm-project/pull/169378