drm/amdgpu: add umc v6_1_1 IP headers

the change introduces IP headers for unified memory controller (umc)

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Dennis Li <dennis.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>