drm/amdgpu/vcn: enable AV1 on both instances

v1 - remove cs parse code (Christian)

On VCN v4_0_6 AV1 is supported on both the instances.
Remove cs IB parse code since explict handling of AV1 schedule is
not required.

Signed-off-by: Saleemkhan Jamadar <saleemkhan.jamadar@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org