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>
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index ebe4544..f409990 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -71,13 +71,12 @@
 	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;
 }
 
 /*