xfs: add more statics & drop some unused functions

A lot more functions could be made static, but they need
forward declarations; this does some easy ones, and also
found a few unused functions in the process.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

fs/xfs/linux-2.6/xfs_super.c

@@ -687,7 +687,7 @@ xfs_barrier_test(
 	return error;
 }
 
-void
+STATIC void
 xfs_mountfs_check_barriers(xfs_mount_t *mp)
 {
 	int error;