[AMDGPU] Support idot2 pattern.
[AMDGPU] Match udot4 pattern.
[AMDGPU] Match udot8 pattern
[AMDGPU] Match signed dot4/8 pattern.
[AMDGPU] Handle the idot8 pattern generated by FE.
[AMDGPU] Promote constant offset to the immediate by finding a new base with 13bit constant offset from the nearby instructions.
[AMDGPU] Removed the unnecessary operand size-check-assert from processBaseWithConstOffset().