[llvm] [NFC][AMDGPU] Assert no bad shift operations will happen (PR #108416)

[Nico Weber via llvm-commits]

nico wrote:

This seems to break building everywhere, eg http://45.33.8.238/linux/148622/step_3.txt

Please take a look and revert for now if it takes a while to fix.

https://github.com/llvm/llvm-project/pull/108416