bcachefs: unregister_shrinker() now safe on not-registered shrinker

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_cache.c

@@ -398,7 +398,6 @@ void bch2_fs_btree_cache_exit(struct bch_fs *c)
 	struct btree *b;
 	unsigned i, flags;
 
-	if (bc->shrink.list.next)
 	unregister_shrinker(&bc->shrink);
 
 	/* vfree() can allocate memory: */

fs/bcachefs/btree_key_cache.c

@@ -955,7 +955,6 @@ void bch2_fs_btree_key_cache_exit(struct btree_key_cache *bc)
 	int cpu;
 #endif
 
-	if (bc->shrink.list.next)
 	unregister_shrinker(&bc->shrink);
 
 	mutex_lock(&bc->lock);