cdc_ncm: flag the u-blox TOBY-L4 as wwan

The u-blox TOBY-L4 is a LTE Advanced (Cat 6) module with HSPA+ and 2G
fallback.

Unlike the TOBY-L2, this module has one single USB layout and exposes
several TTYs for control and a NCM interface for data. Connecting this
module may be done just by activating the desired PDP context with
'AT+CGACT=1,<cid>' and then running DHCP on the NCM interface.

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: David S. Miller <davem@davemloft.net>