Add in the function framework for the processing of LAG events.  Also add
in helper function to perform common tasks.

Add the basis of the process of linking a lower netdev to an upper netdev.
Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
Tested-by: Sujai Buvaneswaran <sujai.buvaneswaran@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>