usb: dwc3: gadget: hold gadget IRQ in dwc->irq_gadget

by holding gadget's IRQ number in dwc->irq_gadget,
it'll be simpler to free_irq() and disable the IRQ
in case an IRQ fires while we are runtime suspended.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 7ba4287..378c14c 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1751,6 +1751,7 @@
 				irq, ret);
 		goto err0;
 	}
+	dwc->irq_gadget = irq;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	if (dwc->gadget_driver) {
@@ -1787,15 +1788,13 @@
 {
 	struct dwc3		*dwc = gadget_to_dwc(g);
 	unsigned long		flags;
-	int			irq;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	__dwc3_gadget_stop(dwc);
 	dwc->gadget_driver	= NULL;
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
-	irq = platform_get_irq(to_platform_device(dwc->dev), 0);
-	free_irq(irq, dwc->ev_buf);
+	free_irq(dwc->irq_gadget, dwc->ev_buf);
 
 	return 0;
 }