USB: Add USB-ID for Multiplex RC serial adapter to cp210x.c

Hi, below patch adds the USB-ID of the serial adapters sold by
Multiplex RC (www.multiplex-rc.de).

Signed-off-by: Malte Schröder <maltesch@gmx.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/cp210x.c

@@ -92,6 +92,7 @@ static const struct usb_device_id id_table[] = {
 	{ USB_DEVICE(0x10C4, 0x818B) }, /* AVIT Research USB to TTL */
 	{ USB_DEVICE(0x10C4, 0x819F) }, /* MJS USB Toslink Switcher */
 	{ USB_DEVICE(0x10C4, 0x81A6) }, /* ThinkOptics WavIt */
+	{ USB_DEVICE(0x10C4, 0x81A9) }, /* Multiplex RC Interface */
 	{ USB_DEVICE(0x10C4, 0x81AC) }, /* MSD Dash Hawk */
 	{ USB_DEVICE(0x10C4, 0x81AD) }, /* INSYS USB Modem */
 	{ USB_DEVICE(0x10C4, 0x81C8) }, /* Lipowsky Industrie Elektronik GmbH, Baby-JTAG */