md/raid5: simplify uninitialization of shrinker

Don't use shrinker.nr_deferred to check whether shrinker was
initialized or not. Now this check was integrated into
unregister_shrinker(), so it is safe to call it against
unregistered shrinker.
Signed-off-by: Aliaksei Karaliou <akaraliou.dev@gmail.com>
Signed-off-by: Shaohua Li <sh.li@alibaba-inc.com>

drivers/md/raid5.c

@@ -6764,9 +6764,7 @@ static void free_conf(struct r5conf *conf)
 
 	log_exit(conf);
 
-	if (conf->shrinker.nr_deferred)
 	unregister_shrinker(&conf->shrinker);
-
 	free_thread_groups(conf);
 	shrink_stripes(conf);
 	raid5_free_percpu(conf);