USB: ftdi_sio: Added custom PID for Synapse Wireless product

commit 4899c054a90439477b24da8977db8d738376fe90 upstream.

Synapse Wireless uses the FTDI VID with a custom PID of 0x9090 for their
SNAP Stick 200 product.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>