drm/amdgpu: add HDP Clock Gating support for yellow carp

HDP MGCG is enabled by default.
Adding AMD_CG_SUPPORT_HDP_MGCG to ensure hdp mgcg enabled.
HDP MGLS need to be enabled by driver.

Signed-off-by: Aaron Liu <aaron.liu@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>