drm/amdgpu: enable VCN0 and VCN1 sriov instances support for Arcturus

v1: compared to bare-metal: sriov support psp loading VCN firmware; only one
encoding ring would be used in each instance.
v2: keep unchange for bare-metal VCN2.5 hw_init, just add a flag with sriov
and also remove multiple lines.
v3: squash in warning fix

Signed-off-by: Jane Jian <Jane.Jian@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>