drm/sched: Remove redundant check

The rq pointer points inside the drm_gpu_scheduler structure. Thus
it can't be NULL.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: c61cdbdbffc1 ("drm/scheduler: Fix hang when sched_entity released")
Signed-off-by: Vladislav Efanov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Luben Tuikov <[e-mail]>
Signed-off-by: Luben Tuikov <[e-mail]>

drivers/gpu/drm/scheduler/sched_main.c

···
 	for (i = DRM_SCHED_PRIORITY_COUNT - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
 		struct drm_sched_rq *rq = &sched->sched_rq[i];
 
-		if (!rq)
-			continue;
-
 		spin_lock(&rq->lock);
 		list_for_each_entry(s_entity, &rq->entities, list)
 			/*