btrfs: make btrfs_set_root_node void

This is fairly trivial - btrfs_set_root_node() - always returns zero so we
can just make it void.  All callers ignore the return code now anyway.  I
also made sure to check that none of the functions that
btrfs_set_root_node() calls returns an error that we might have needed to
catch and pass back.
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

@@ -2406,8 +2406,8 @@ int btrfs_find_last_root(struct btrfs_root *root, u64 objectid, struct
 			 btrfs_root_item *item, struct btrfs_key *key);
 int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid);
 int btrfs_find_orphan_roots(struct btrfs_root *tree_root);
-int btrfs_set_root_node(struct btrfs_root_item *item,
-			struct extent_buffer *node);
+void btrfs_set_root_node(struct btrfs_root_item *item,
+			 struct extent_buffer *node);
 void btrfs_check_and_init_root_item(struct btrfs_root_item *item);
 
 /* dir-item.c */

fs/btrfs/root-tree.c

@@ -71,13 +71,12 @@ int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
 	return ret;
 }
 
-int btrfs_set_root_node(struct btrfs_root_item *item,
-			struct extent_buffer *node)
+void btrfs_set_root_node(struct btrfs_root_item *item,
+			 struct extent_buffer *node)
 {
 	btrfs_set_root_bytenr(item, node->start);
 	btrfs_set_root_level(item, btrfs_header_level(node));
 	btrfs_set_root_generation(item, btrfs_header_generation(node));
-	return 0;
 }
 
 /*