f2fs: correct spelling mistake

correct spelling mistake for "nunmber"
Signed-off-by: Zeng Guangyue <zengguangyue@hisilicon.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

include/linux/f2fs_fs.h

@@ -285,7 +285,7 @@ enum {
 
 struct node_footer {
 	__le32 nid;		/* node id */
-	__le32 ino;		/* inode nunmber */
+	__le32 ino;		/* inode number */
 	__le32 flag;		/* include cold/fsync/dentry marks and offset */
 	__le64 cp_ver;		/* checkpoint version */
 	__le32 next_blkaddr;	/* next node page block address */