[XFS] Compat ioctl handler for handle operations

32bit struct xfs_fsop_handlereq has different size and offsets (due to
pointers). TODO: case XFS_IOC_{FSSETDM,ATTRLIST,ATTRMULTI}_BY_HANDLE still
not handled.

SGI-PV: 967354
SGI-Modid: xfs-linux-melb:xfs-kern:29101a

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