drm/amdgpu/vce4: move mm table constructions functions into mmsch header file

Move mm table construction functions into mmsch header file so that
UVD can reuse it.

Signed-off-by: Frank Min <Frank.Min@amd.com>
Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>