usb: dwc3: gadget: skip Set/Clear Halt when invalid

At least macOS seems to be sending
ClearFeature(ENDPOINT_HALT) to endpoints which
aren't Halted. This makes DWC3's CLEARSTALL command
time out which causes several issues for the driver.

Instead, let's just return 0 and bail out early.

Cc: <stable@vger.kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -1379,6 +1379,9 @@ int __dwc3_gadget_ep_set_halt(struct dwc3_ep *dep, int value, int protocol)
 		unsigned transfer_in_flight;
 		unsigned started;
 
+		if (dep->flags & DWC3_EP_STALL)
+			return 0;
+
 		if (dep->number > 1)
 			trb = dwc3_ep_prev_trb(dep, dep->trb_enqueue);
 		else
@@ -1400,6 +1403,8 @@ int __dwc3_gadget_ep_set_halt(struct dwc3_ep *dep, int value, int protocol)
 		else
 			dep->flags |= DWC3_EP_STALL;
 	} else {
+		if (!(dep->flags & DWC3_EP_STALL))
+			return 0;
 
 		ret = dwc3_send_clear_stall_ep_cmd(dep);
 		if (ret)