cdc_ether: add Novatel USB551L device IDs for FLAG_WWAN

commit 4e6304b8420aba5311ba21fd68dab2924ae4d91a upstream.

Needs to be tagged with FLAG_WWAN, which since it has generic
descriptors, won't happen if we don't override the generic
driver info.

Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Dan Williams <dcbw@redhat.com>
Acked-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>