usbnet/cdc_ncm: add missing .reset_resume hook

This avoids messages like this after suspend:

   cdc_ncm 2-1.4:1.6: no reset_resume for driver cdc_ncm?
   cdc_ncm 2-1.4:1.7: no reset_resume for driver cdc_ncm?
   cdc_ncm 2-1.4:1.6: usb0: unregister 'cdc_ncm' usb-0000:00:1d.0-1.4, CDC NCM

This is important for the Ericsson F5521gw GSM/UMTS modem.
Otherwise modemmanager looses the fact that the cdc_ncm and cdc_acm devices
belong together.

The cdc_ether module does the same.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>