Add support for the management port device id.  This is to
capture the device and set it up for devlink use, but not set
it up for network operations.  We still use a netdev object
in order to use the napi infrasucture for processing adminq
and notifyq messages, we just don't register the netdev.
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>