[media] gspca - main: isoc mode devices are never low speed

Quoting from the official usb 20 spec:
"5.6.4 Isochronous Transfer Bus Access Constraints

Isochronous transfers can only be used by full-speed and high-speed devices."

This means that for code paths which are isoc mode only, we don't need to
check for the device being low speed, simplifying the code.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/gspca.c

@@ -818,9 +818,6 @@ static int create_urbs(struct gspca_dev *gspca_dev,
 						    ep->desc.bEndpointAddress);
 			urb->transfer_flags = URB_ISO_ASAP
 					| URB_NO_TRANSFER_DMA_MAP;
-			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;