usb: dwc2: gadget: Fix transfer stop programming for out endpoint

According DWC-OTG databook, "GOUTNakEff" is read only and can be
cleared only by "DCTL.CGOUTNak", but here we do not need to clear
it because DWC-OTG programming guide says that before disabling
any OUT endpoint, the application must enable Global OUT NAK mode,
so if this mode is enabled we can continue without this step.

Tested-by: John Keeping <john@metanate.com>
Signed-off-by: Vardan Mikayelyan <mvardan@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>