drm/amdgpu: enable VCN3.0 PG and CG for dimgrey_cavefish

Enable VCN3.0 PG and CG for dimgrey_cavefish

Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>