staging: dwc2: fix some functions to return a proper error code

Fix some functions called by dwc2_hcd_qtd_add() to return either
a proper error code or 0, instead of somewhat random values.
Then change the caller of dwc2_hcd_qtd_add() to just check the
return value for 0.
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dwc2/hcd.c

@@ -369,7 +369,7 @@ static int dwc2_hcd_urb_enqueue(struct dwc2_hsotg *hsotg,
 	dwc2_hcd_qtd_init(qtd, urb);
 	retval = dwc2_hcd_qtd_add(hsotg, qtd, (struct dwc2_qh **)ep_handle,
 				  mem_flags);
-	if (retval < 0) {
+	if (retval) {
 		dev_err(hsotg->dev,
 			"DWC OTG HCD URB Enqueue failed adding QTD. Error status %d\n",
 			retval);
@@ -378,7 +378,7 @@ static int dwc2_hcd_urb_enqueue(struct dwc2_hsotg *hsotg,
 	}
 
 	intr_mask = readl(hsotg->regs + GINTMSK);
-	if (!(intr_mask & GINTSTS_SOF) && retval == 0) {
+	if (!(intr_mask & GINTSTS_SOF)) {
 		enum dwc2_transaction_type tr_type;
 
 		if (qtd->qh->ep_type == USB_ENDPOINT_XFER_BULK &&
@@ -396,7 +396,7 @@ static int dwc2_hcd_urb_enqueue(struct dwc2_hsotg *hsotg,
 		spin_unlock_irqrestore(&hsotg->lock, flags);
 	}
 
-	return retval;
+	return 0;
 }
 
 /* Must be called with interrupt disabled and spinlock held */

drivers/staging/dwc2/hcd_queue.c

@@ -354,7 +354,7 @@ static int dwc2_find_single_uframe(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 			return i;
 		}
 	}
-	return -1;
+	return -ENOSPC;
 }
 
 /*
@@ -413,7 +413,7 @@ static int dwc2_find_multi_uframe(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 				continue;
 		}
 	}
-	return -1;
+	return -ENOSPC;
 }
 
 static int dwc2_find_uframe(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
@@ -487,12 +487,12 @@ static int dwc2_schedule_periodic(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 			frame = status - 1;
 
 		/* Set the new frame up */
-		if (frame > -1) {
+		if (frame >= 0) {
 			qh->sched_frame &= ~0x7;
 			qh->sched_frame |= (frame & 7);
 		}
 
-		if (status != -1)
+		if (status > 0)
 			status = 0;
 	} else {
 		status = dwc2_periodic_channel_available(hsotg);