AMDGPU: Fix asserts on invalid register ranges

If the requested SGPR was not actually aligned, it was
accepted and rounded down instead of rejected.

Also fix an assert if the range is an invalid size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252009 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed