cdc_ether: flag the Cinterion AHS8 modem by gemalto as WWAN

The Cinterion AHS8 is a 3G device with one embedded WWAN interface
using cdc_ether as a driver.

The modem is controlled via AT commands through the exposed TTYs.

AT+CGDCONT write command can be used to activate or deactivate a WWAN
connection for a PDP context defined with the same command. UE
supports one WWAN adapter.

Signed-off-by: Bassem Boubaker <bassem.boubaker@actia.fr>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>