Initial implementation of notification handlers. For now this is just
stub.
So that we can move forward and add prestera_router_hw's objects
manipulations.

We support several addresses on interface. We just have nothing to do for
second address, because rif is already enabled on this interface, after
first one.
Co-developed-by: Taras Chornyi <tchornyi@marvell.com>
Signed-off-by: Taras Chornyi <tchornyi@marvell.com>
Co-developed-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: Yevhen Orlov <yevhen.orlov@plvision.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>