ionic: Add basic lif support

The LIF is the Logical Interface, which represents the external
connections.  The NIC can multiplex many LIFs to a single port,
but in most setups, LIF0 is the primary control for the port.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>