xfs: remove if_rdev

We can simply use the i_rdev field in the Linux inode and just convert
to and from the XFS dev_t when reading or logging/writing the inode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_inode_item.c

@@ -222,7 +222,7 @@ xfs_inode_item_format_data_fork(
 		iip->ili_fields &=
 			~(XFS_ILOG_DDATA | XFS_ILOG_DBROOT | XFS_ILOG_DEXT);
 		if (iip->ili_fields & XFS_ILOG_DEV)
-			ilf->ilf_u.ilfu_rdev = ip->i_df.if_u2.if_rdev;
+			ilf->ilf_u.ilfu_rdev = sysv_encode_dev(VFS_I(ip)->i_rdev);
 		break;
 	default:
 		ASSERT(0);