usb: dwc3: gadget: return errors from __dwc3_gadget_start_isoc()

Sometimes, errors happen when kicking transfers from
__dwc3_gadget_start_isoc(). In those cases, we need to pass along the
error so gadget driver can make informed decisions.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
1 file changed