[XFS] Compat ioctl handler for XFS_IOC_FSGEOMETRY_V1.

i386 struct xfs_fsop_geom_v1 has no padding after the last member, so the
size is different.

SGI-PV: 967354
SGI-Modid: xfs-linux-melb:xfs-kern:29100a

Signed-off-by: Michal Marek <mmarek@suse.cz>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>