[XFS] Fix potential overflow in xfs_iomap_t delta for very large extents

SGI-PV: 945311
SGI-Modid: xfs-linux-melb:xfs-kern:201708a

Signed-off-by: Eric Sandeen <sandeen@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
1 file changed