USB: log an error message when USB enumeration fails

This patch (as1077) logs an error message whenever the kernel is
unable to enumerate a new USB device.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hub.c

@@ -2708,6 +2708,7 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
 		if ((status == -ENOTCONN) || (status == -ENOTSUPP))
 			break;
 	}
+	dev_err(hub_dev, "unable to enumerate USB device on port %d\n", port1);
 
 done:
 	hub_port_disable(hub, port1, 1);