[XFS] fix old xfs_setattr mis-merge from irix; mostly harmless esp if not

using xfs rt

SGI-PV: 944632
SGI-Modid: xfs-linux:xfs-kern:200983a

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