ext4: use DEFINE_MUTEX() for mutex lock

mutex lock can be initialized automatically with DEFINE_MUTEX()
rather than explicitly calling mutex_init().
Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Link: https://lore.kernel.org/r/20201224132244.30907-1-zhengyongjun3@huawei.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -59,7 +59,7 @@
 #include <trace/events/ext4.h>
 
 static struct ext4_lazy_init *ext4_li_info;
-static struct mutex ext4_li_mtx;
+static DEFINE_MUTEX(ext4_li_mtx);
 static struct ratelimit_state ext4_mount_msg_ratelimit;
 
 static int ext4_load_journal(struct super_block *, struct ext4_super_block *,
@@ -6667,7 +6667,6 @@ static int __init ext4_init_fs(void)
 
 	ratelimit_state_init(&ext4_mount_msg_ratelimit, 30 * HZ, 64);
 	ext4_li_info = NULL;
-	mutex_init(&ext4_li_mtx);
 
 	/* Build-time check for flags consistency */
 	ext4_check_flag_values();