USB: serial: option: add support for Novatel MiFi USB620L

Also known as Verizon U620L.

The device is modeswitched from 1410:9020 to 1410:9022 by selecting the
4th USB configuration:

 $ sudo usb_modeswitch –v 0x1410 –p 0x9020 –u 4

This configuration provides a ECM interface as well as TTYs ('Enterprise
Mode' according to the U620 Linux integration guide).

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>