usb: dwc3: gadget: Fix PCM1 for ISOC EP with ep->mult less than 3

For isochronous endpoints with ep->mult less than 3, PCM1 value of
trb->size in set incorrectly.
For ep->mult = 2, this is set to 0/-1 and for ep->mult = 1, this is
set to -2. This is because the initial mult is set to ep->mult - 1
instead of 2.
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -912,7 +912,7 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *dep, struct dwc3_trb *trb,
 			 */
 			if (speed == USB_SPEED_HIGH) {
 				struct usb_ep *ep = &dep->endpoint;
-				unsigned int mult = ep->mult - 1;
+				unsigned int mult = 2;
 				unsigned int maxp = usb_endpoint_maxp(ep->desc);
 
 				if (length <= (2 * maxp))