drm/amdgpu: Check RRMT status for VCN v4.0.3

RRMT could get dynamically enabled/disabled by PSP firmware. Read the
status from register for reading RRMT status. For VFs, this is not
accessible, hence assume that it's always disabled for now.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>