of/flattree: Drop an uninteresting message to pr_debug level

This message looks like an error (which it isn't) when booting with a
flattened device tree.  Remove the message from normal kernel builds.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

fs/proc/proc_devtree.c

@@ -233,7 +233,7 @@ void __init proc_device_tree_init(void)
 		return;
 	root = of_find_node_by_path("/");
 	if (root == NULL) {
-		printk(KERN_ERR "/proc/device-tree: can't find root\n");
+		pr_debug("/proc/device-tree: can't find root\n");
 		return;
 	}
 	proc_device_tree_add_node(root, proc_device_tree);