usb: dwc3: gadget: clear stall when disabling endpoint

so it seems like DWC3 IP doesn't clear stalls
automatically when we disable an endpoint, because
of that, we _must_ make sure stalls are cleared
before clearing the proper bit in DALEPENA register.

Cc: <stable@vger.kernel.org> # v3.4+
Reported-by: NJohannes Stezenbach <js@sig21.net>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -608,6 +608,10 @@ static int __dwc3_gadget_ep_disable(struct dwc3_ep *dep)
 
 	dwc3_remove_requests(dwc, dep);
 
+	/* make sure HW endpoint isn't stalled */
+	if (dep->flags & DWC3_EP_STALL)
+		__dwc3_gadget_ep_set_halt(dep, 0);
+
 	reg = dwc3_readl(dwc->regs, DWC3_DALEPENA);
 	reg &= ~DWC3_DALEPENA_EP(dep->number);
 	dwc3_writel(dwc->regs, DWC3_DALEPENA, reg);