[XFS] Move XFS_BMAP_SANITY_CHECK out of line.

Move the XFS_BMAP_SANITY_CHECK macro out of line and make it a properly
typed function. Also pass the xfs_buf for the btree block instead of just
the btree block header, as we will need some additional information for it
to implement CRC checking of btree blocks.

SGI-PV: 988146

SGI-Modid: xfs-linux-melb:xfs-kern:32301a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Donald Douwsma <donaldd@sgi.com>
Signed-off-by: David Chinner <david@fromorbit.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>