drm/amdgpu: error out on entity with no run queue

Disabled HW IP's entity initialized with NULL rq. We should not
process any submit request from userspace for a disabled HW IP.

Signed-off-by: Nirmoy Das <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c

···
 		if (parser->entity && parser->entity != entity)
 			return -EINVAL;
 
+		/* Return if there is no run queue associated with this entity.
+		 * Possibly because of disabled HW IP*/
+		if (entity->rq == NULL)
+			return -EINVAL;
+
 		parser->entity = entity;
 
 		ring = to_amdgpu_ring(entity->rq->sched);