greybus: interface: fix type in enable error message

Fix type of PTR_ERR in an interface-enable error message.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/interface.c

@@ -564,7 +564,7 @@ int gb_interface_enable(struct gb_interface *intf)
 	/* Establish control connection */
 	control = gb_control_create(intf);
 	if (IS_ERR(control)) {
-		dev_err(&intf->dev, "failed to create control device: %lu\n",
+		dev_err(&intf->dev, "failed to create control device: %ld\n",
 				PTR_ERR(control));
 		return PTR_ERR(control);
 	}