usb: dwc3: skip interrupt when ep disabled

In case EP disabled pass only EPCPLT command
to be handled. In other case we could hit
Bug like below.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000003
IP:
[<ffffffff81673428>] dwc3_thread_interrupt+0x11c8/0x1790

while dep->endpoint.desc is NULL.
Signed-off-by: Janusz Dziedzic <januszx.dziedzic@linux.intel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -2232,10 +2232,15 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
 
 	dep = dwc->eps[epnum];
 
-	if (!(dep->flags & DWC3_EP_ENABLED) &&
-	    !(dep->flags & DWC3_EP_END_TRANSFER_PENDING))
+	if (!(dep->flags & DWC3_EP_ENABLED)) {
+		if (!(dep->flags & DWC3_EP_END_TRANSFER_PENDING))
 			return;
 
+		/* Handle only EPCMDCMPLT when EP disabled */
+		if (event->endpoint_event != DWC3_DEPEVT_EPCMDCMPLT)
+			return;
+	}
+
 	if (epnum == 0 || epnum == 1) {
 		dwc3_ep0_interrupt(dwc, event);
 		return;