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>

drivers/usb/dwc3/core.h

@@ -730,6 +730,7 @@ struct dwc3_scratchpad_array {
  * @regs: base address for our registers
  * @regs_size: address space size
  * @fladj: frame length adjustment
+ * @irq_gadget: peripheral controller's IRQ number
  * @nr_scratch: number of scratch buffers
  * @u1u2: only used on revisions <1.83a for workaround
  * @maximum_speed: maximum speed requested (mainly for testing purposes)
@@ -837,6 +838,7 @@ struct dwc3 {
 	enum usb_dr_mode	dr_mode;
 
 	u32			fladj;
+	u32			irq_gadget;
 	u32			nr_scratch;
 	u32			u1u2;
 	u32			maximum_speed;

drivers/usb/dwc3/gadget.c

@@ -1751,6 +1751,7 @@ static int dwc3_gadget_start(struct usb_gadget *g,
 				irq, ret);
 		goto err0;
 	}
+	dwc->irq_gadget = irq;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	if (dwc->gadget_driver) {
@@ -1787,15 +1788,13 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
 {
 	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;
 }