f2fs: fix typos in code comments

lengh -> length
Signed-off-by: NGeliang Tang <geliangtang@gmail.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

include/linux/f2fs_fs.h

@@ -187,7 +187,7 @@ struct f2fs_orphan_block {
 struct f2fs_extent {
 	__le32 fofs;		/* start file offset of the extent */
 	__le32 blk;		/* start block address of the extent */
-	__le32 len;		/* lengh of the extent */
+	__le32 len;		/* length of the extent */
 } __packed;
 
 #define F2FS_NAME_LEN		255
@@ -512,7 +512,7 @@ typedef __le32	f2fs_hash_t;
 struct f2fs_dir_entry {
 	__le32 hash_code;	/* hash code of file name */
 	__le32 ino;		/* inode number */
-	__le16 name_len;	/* lengh of file name */
+	__le16 name_len;	/* length of file name */
 	__u8 file_type;		/* file type */
 } __packed;