[llvm] [AMDGPU] Fix bit-packing condition in LiveRegOptimizer (PR #201520)

[Steffen Larsen via llvm-commits]

steffenlarsen wrote:

Note: Another solution to the problem is made in https://github.com/llvm/llvm-project/pull/196609. If people prefer, we can go with that solution instead.

https://github.com/llvm/llvm-project/pull/201520