block: Remove redundant parent blkcg_gp check in check_scale_change

Function blkcg_iolatency_throttle will make sure blkg->parent is not
NULL before calls check_scale_change. And function check_scale_change
is only called in blkcg_iolatency_throttle.
Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20221018111240.22612-2-shikemeng@huawei.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-iolatency.c

@@ -403,9 +403,6 @@ static void check_scale_change(struct iolatency_grp *iolat)
 	u64 scale_lat;
 	int direction = 0;
 
-	if (lat_to_blkg(iolat)->parent == NULL)
-		return;
-
 	parent = blkg_to_lat(lat_to_blkg(iolat)->parent);
 	if (!parent)
 		return;