drm/amdgpu: load balance VCN3 decode as well v8

drm/amdgpu: load balance VCN3 decode as well v8

Add VCN3 IB parsing to figure out to which instance we can send the
stream for decode.

v2: remove VCN instance limit as well, fix amdgpu_cs_find_mapping,
    check supported formats instead of unsupported.
v3: fix typo and error handling
v4: make sure the message BO is CPU accessible
v5: fix addr calculation once more
v6: only check message buffers
v7: fix constant and use defines
v8: fix create msg calculation

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Sonny Jiang <sonny.jiang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>