usb: s3c-otg: Rename USB_GADGET_S3C_UDC_OTG* to USB_GADGET_DWC2_OTG*

usb: s3c-otg: Rename USB_GADGET_S3C_UDC_OTG* to USB_GADGET_DWC2_OTG*

The s3c-otg IP block is in fact a DWC2 OTG one, so finally rename the
config option to make it less misleading. No functional change, just
a mechanical change done using the following script:

  git grep USB_GADGET_S3C_UDC_OTG | cut -d : -f 1 | sort -u | \
  while read line ; do
    sed -i "s/USB_GADGET_S3C_UDC_OTG/USB_GADGET_DWC2_OTG/g" $line ;
  done

Signed-off-by: Marek Vasut <marex@denx.de>