[XFS] Remove a bunch of unused functions from XFS.

Patch provided by Eric Sandeen (sandeen@sandeen.net).

SGI-PV: 960897
SGI-Modid: xfs-linux-melb:xfs-kern:28038a

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>