These are equivalent to the xfs_btree_* versions, and the only remaining
caller can be switched to the generic one after they are exported. Also
remove some now dead infrastructure in xfs_bmap_btree.c.

SGI-PV: 985583

SGI-Modid: xfs-linux-melb:xfs-kern:32207a
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>
Signed-off-by: NBill O'Donnell <billodo@sgi.com>
Signed-off-by: NDavid Chinner <david@fromorbit.com>