[media] gspca - main: Fix the isochronous transfer interval

For USB speeds different of 'low', the bInterval value is logarithmic.
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/gspca.c

@@ -754,7 +754,10 @@ static int create_urbs(struct gspca_dev *gspca_dev,
 						    ep->desc.bEndpointAddress);
 			urb->transfer_flags = URB_ISO_ASAP
 					| URB_NO_TRANSFER_DMA_MAP;
-			urb->interval = ep->desc.bInterval;
+			if (gspca_dev->dev->speed == USB_SPEED_LOW)
+				urb->interval = ep->desc.bInterval;
+			else
+				urb->interval = 1 << (ep->desc.bInterval - 1);
 			urb->complete = isoc_irq;
 			urb->number_of_packets = npkt;
 			for (i = 0; i < npkt; i++) {