xfs: constify xfs_item_ops

The log item ops aren't nessecarily the biggest exploit vector, but marking
them const is easy enough.  Also remove the unused xfs_item_ops_t typedef
while we're at it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>

diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
index 78c9039..3f7bf45 100644
--- a/fs/xfs/xfs_log.h
+++ b/fs/xfs/xfs_log.h
@@ -137,7 +137,7 @@
 void	xfs_log_item_init(struct xfs_mount	*mp,
 			struct xfs_log_item	*item,
 			int			type,
-			struct xfs_item_ops	*ops);
+			const struct xfs_item_ops *ops);
 
 xfs_lsn_t xfs_log_done(struct xfs_mount *mp,
 		       struct xlog_ticket *ticket,