USB: serial: ftdi_sio: Vardaan USB RS422/485 converter PID added

Add the PID for the Vardaan Enterprises VEUSB422R3 USB to RS422/485
converter. It uses the same chip as the FTDI_8U232AM_PID 0x6001.

This should also work with the stable branches for:
2.6.31, 2.6.32, 2.6.33, 2.6.34, 2.6.35, 2.6.36

Signed-off-by: Jacques Viviers <jacques.viviers@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>