AMDGPU: Add test for temporal divergence introduced by machine-sink

Introduced by 5b657f50 that moved
LICM after AMDGPUCodeGenPrepare. Some instructions are no longer
sunk during ir optimizations but in machine-sinking instead.
If vgpr instruction used sgpr defined inside the cycle is sunk outside
of the cycle we end up with not-handled case of temporal divergence.
Add test for theoretical case when SALU instruction (represents
uniform value) is sunk outside of the cycle.
Add a test when SALU instruction can be sunk if it edits lane mask.