USB: option: add device ID for SpeedUp SU9800 usb 3g modem

Reported by Alif Mubarak Ahmad:

This device vendor and product id is 1c9e:9800
It is working as serial interface with generic usbserial driver.
I thought it is more suitable to use usbserial option driver, which has
better capability distinguishing between modem serial interface and
micro sd storage interface.

[ johan: style changes ]

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Tested-by: Alif Mubarak Ahmad <alive4ever@live.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>