usb: gadget: f_acm: don't disable disabled EP

Make debugging real problems easier by not trying to disable an EP that
was not yet enabled.
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/gadget/function/f_acm.c

@@ -425,9 +425,11 @@ static int acm_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 	/* we know alt == 0, so this is an activation or a reset */
 
 	if (intf == acm->ctrl_id) {
-		dev_vdbg(&cdev->gadget->dev,
-				"reset acm control interface %d\n", intf);
-		usb_ep_disable(acm->notify);
+		if (acm->notify->enabled) {
+			dev_vdbg(&cdev->gadget->dev,
+					"reset acm control interface %d\n", intf);
+			usb_ep_disable(acm->notify);
+		}
 
 		if (!acm->notify->desc)
 			if (config_ep_by_speed(cdev->gadget, f, acm->notify))