drm/amdgpu: move UVD/VCE and VCN structure out from union

With the enablement of VCN Dec and Enc from user space, User space queries
kernel for the IP information, if HW has UVD/VCE, the info comes from these
IP blocks, but this could end up mis-interpret for VCN when they are in the
union, the other way same when HW with VCN block.

Signed-off-by: Leo Liu <leo.liu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Fixes: 95d0906f ("drm/amdgpu: add initial vcn support and decode tests")
Cc: stable@vger.kernel.org
Reviewed-and-Tested-by: Michel Dänzer <michel.daenzer@amd.com>