drm/amdgpu: Update ring scheduler info as needed

Not all rings have scheduler associated. Only update scheduler data for
rings with scheduler. It could result in out of bound access as total
rings are more than those associated with particular IPs.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: James Zhu <James.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>