dm: Provide better debugging when a device fails to bind

All devices should bind without error. But when they don't, they can cause
driver model init to fail. A real situation where this can happen is when
there is a missing uclass.

Add a debug() call to dm_scan_fdt_node to make this easier to track.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/core/root.c

@@ -162,8 +162,11 @@ int dm_scan_fdt_node(struct udevice *parent, const void *blob, int offset,
 			continue;
 		}
 		err = lists_bind_fdt(parent, blob, offset, NULL);
-		if (err && !ret)
+		if (err && !ret) {
 			ret = err;
+			debug("%s: ret=%d\n", fdt_get_name(blob, offset, NULL),
+			      ret);
+		}
 	}
 
 	if (ret)