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

commit ffb80fc6 upstream.

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.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/dwc3/gadget.c

@@ -1346,6 +1346,9 @@ int __dwc3_gadget_ep_set_halt(struct dwc3_ep *dep, int value, int protocol)
 	memset(&params, 0x00, sizeof(params));
 
 	if (value) {
+		if (dep->flags & DWC3_EP_STALL)
+			return 0;
+
 		if (!protocol && ((dep->direction && dep->flags & DWC3_EP_BUSY) ||
 				(!list_empty(&dep->req_queued) ||
 				 !list_empty(&dep->request_list)))) {
@@ -1362,6 +1365,9 @@ 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_gadget_ep_cmd(dwc, dep->number,
 			DWC3_DEPCMD_CLEARSTALL, &params);
 		if (ret)