ext4 crypto: release crypto resource on module exit

Crypto resource should be released when ext4 module exits, otherwise
it will cause memory leak.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -5645,6 +5645,7 @@ static int __init ext4_init_fs(void)
 
 static void __exit ext4_exit_fs(void)
 {
+	ext4_exit_crypto();
 	ext4_destroy_lazyinit_thread();
 	unregister_as_ext2();
 	unregister_as_ext3();