1) Remove serial-usb device from the AVM 7270.

    usb_endpoint  \  usb_endpoint  \   tty   \  usb_endpoint  \ usb-serial \ usb_device \
   usbdev1.4_ep81 / usbdev1.4_ep02 / ttyUSB0 / usbdev1.4_ep83 /   ttyUSB0  /  usbdev1.4 /
                                     ---+---
                                        !
   unload pl2303 driver ----------------+

     usb   \ usb \ usb_endpoint
   1-1:1.0 / 1-1 / usbdev1.4_ep00


2) Unload pl2303 module.

   drivers \ drivers \ module \  drivers  \   bus   \   bus   \    bus     \ module
    pl2303 /  pl2303 / pl2303 / usbserial / drivers / devices / usb-serial / usbserial