[XFS] add xfs_btree_check_lptr_disk variant which handles endian

conversion

SGI-PV: 954580
SGI-Modid: xfs-linux-melb:xfs-kern:26558a

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>

diff --cc fs/xfs/xfs_bmap.c
Simple merge

diff --cc fs/xfs/xfs_bmap_btree.c
Simple merge

diff --cc fs/xfs/xfs_btree.h
Simple merge