drm/amdgpu: Add log info for umc_v12_0

Add log info for umc_v12_0.

v2:
 Delete redundant logs.

Signed-off-by: YiPeng Chai <YiPeng.Chai@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>