ext4: sync up block group descriptor with e2fsprogs.

This patch extends bg_itable_unused of ext4 group descriptor
from 16bit into 32bit. In order to add bg_itable_unused_hi into
struct ext4_group_desc, some extra fields which are already introduced into
e2fsprogs are also added in for consistency.
Signed-off-by: Coly Li <coyli@suse.de>
Cc: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>

include/linux/ext4_fs.h

@@ -118,6 +118,11 @@ struct ext4_group_desc
 	__le32	bg_block_bitmap_hi;	/* Blocks bitmap block MSB */
 	__le32	bg_inode_bitmap_hi;	/* Inodes bitmap block MSB */
 	__le32	bg_inode_table_hi;	/* Inodes table block MSB */
+	__le16	bg_free_blocks_count_hi;/* Free blocks count MSB */
+	__le16	bg_free_inodes_count_hi;/* Free inodes count MSB */
+	__le16	bg_used_dirs_count_hi;	/* Directories count MSB */
+	__le16	bg_itable_unused_hi;	/* Unused inodes count MSB */
+	__u32	bg_reserved2[3];
 };
 
 #define EXT4_BG_INODE_UNINIT	0x0001 /* Inode table/bitmap not in use */