xfs_bmap_count_leaves and xfs_bmap_disk_count_leaves always return always
0, make them void.

SGI-PV: 981498

SGI-Modid: xfs-linux-melb:xfs-kern:31844a
Signed-off-by: Ruben Porras <ruben.porras@linworks.de>
Signed-off-by: Donald Douwsma <donaldd@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>