usb: dwc3: gadget: use generic map/unmap routines

those routines have everything we need to map/unmap
USB requests and it's better to use them.

In order to achieve that, we had to add a simple
change on how we allocate and use our setup buffer;
we cannot allocate it from coherent anymore otherwise
the generic map/unmap routines won't be able to easily
know that the GetStatus request already has a DMA
address.

Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 2f51de5..24137d8 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -309,7 +309,7 @@
 	dep = dwc->eps[0];
 	dwc->ep0_usb_req.dep = dep;
 	dwc->ep0_usb_req.request.length = sizeof(*response_pkt);
-	dwc->ep0_usb_req.request.dma = dwc->setup_buf_addr;
+	dwc->ep0_usb_req.request.buf = dwc->setup_buf;
 	dwc->ep0_usb_req.request.complete = dwc3_ep0_status_cmpl;
 
 	return __dwc3_gadget_ep0_queue(dep, &dwc->ep0_usb_req);
@@ -686,7 +686,12 @@
 				DWC3_TRBCTL_CONTROL_DATA);
 	} else if ((req->request.length % dep->endpoint.maxpacket)
 			&& (event->endpoint_number == 0)) {
-		dwc3_map_buffer_to_dma(req);
+		ret = usb_gadget_map_request(&dwc->gadget, &req->request,
+				event->endpoint_number);
+		if (ret) {
+			dev_dbg(dwc->dev, "failed to map request\n");
+			return;
+		}
 
 		WARN_ON(req->request.length > dep->endpoint.maxpacket);
 
@@ -701,7 +706,12 @@
 				dwc->ep0_bounce_addr, dep->endpoint.maxpacket,
 				DWC3_TRBCTL_CONTROL_DATA);
 	} else {
-		dwc3_map_buffer_to_dma(req);
+		ret = usb_gadget_map_request(&dwc->gadget, &req->request,
+				event->endpoint_number);
+		if (ret) {
+			dev_dbg(dwc->dev, "failed to map request\n");
+			return;
+		}
 
 		ret = dwc3_ep0_start_trans(dwc, event->endpoint_number,
 				req->request.dma, req->request.length,