xfs: move lru refs to the btree ops structure

Move the btree buffer LRU refcount to the btree ops structure so that we
can eliminate the last bc_btnum switch in the generic btree code.  We're
about to create repair-specific btree types, and we don't want that
stuff cluttering up libxfs.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/libxfs/xfs_refcount_btree.c b/fs/xfs/libxfs/xfs_refcount_btree.c
index 36e7b26..eaed951 100644
--- a/fs/xfs/libxfs/xfs_refcount_btree.c
+++ b/fs/xfs/libxfs/xfs_refcount_btree.c
@@ -321,6 +321,8 @@ const struct xfs_btree_ops xfs_refcountbt_ops = {
 	.rec_len		= sizeof(struct xfs_refcount_rec),
 	.key_len		= sizeof(struct xfs_refcount_key),
 
+	.lru_refs		= XFS_REFC_BTREE_REF,
+
 	.dup_cursor		= xfs_refcountbt_dup_cursor,
 	.set_root		= xfs_refcountbt_set_root,
 	.alloc_block		= xfs_refcountbt_alloc_block,