USB: serial: ftdi_sio: add support for E+H FXA291

USB: serial: ftdi_sio: add support for E+H FXA291

The Commubox FXA291 by Endress+Hauser AG is a USB serial converter
based on FT232B which is used to communicate with field devices.

It enumerates using the FTDI vendor ID and a custom PID.

usb 1-9: New USB device found, idVendor=0403, idProduct=e510, bcdDevice= 4.00
usb 1-9: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 1-9: Product: FXA291
usb 1-9: Manufacturer: Endress+Hauser
usb 1-9: SerialNumber: 00000000
ftdi_sio 1-9:1.0: FTDI USB Serial Device converter detected
usb 1-9: Detected FT232B
usb 1-9: FTDI USB Serial Device converter now attached to ttyUSB0

Signed-off-by: Tim Pambor <timpambor@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>