blk-cgroup: remove the !bdi->dev check in blkg_dev_name

bdi_dev_name already performs the same check.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230203150400.3199230-6-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-cgroup.c

@@ -572,7 +572,7 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css,
 
 const char *blkg_dev_name(struct blkcg_gq *blkg)
 {
-	if (!blkg->q->disk || !blkg->q->disk->bdi->dev)
+	if (!blkg->q->disk)
 		return NULL;
 	return bdi_dev_name(blkg->q->disk->bdi);
 }