[XFS] remove bogus INT_GET on u8 variables in xfs_dir2_block.c

SGI-PV: 943272
SGI-Modid: xfs-linux-melb:xfs-kern:25496a

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