USB: serial: sierra: Add support for Sierra Wireless AirCard 320U modem

commit 19a3dd1575e954e8c004413bee3e12d3962f2525 upstream.

Add support for Sierra Wireless AirCard 320U modem

Signed-off-by: Tomas Cassidy <tomas.cassidy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>