cdc_ether: flag the Cinterion PLS8 modem by gemalto as WWAN

The Cinterion PL8 is an LTE modem with 2 possible WWAN interfaces.

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

    AT^SWWAN write command can be used to activate or deactivate a WWAN
    connection for a PDP context defined with AT+CGDCONT. UE supports
    two WWAN adapter. Both WWAN adapters can be activated a the same time

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>