[AMDGPU] Limit memory scope for scratch, LDS and GDS

Changes for AMD GPU SIMemoryLegalizer:

- Limit the memory scope to maximum supported by the scratch, LDS and
  GDS address spaces.

- Improve assertion checking.

- Correct toSIAtomicScope argument name.

Reviewed By: rampitec

Differential Revision: https://reviews.llvm.org/D96643