ipmr: Send FIB notifications on MFC and VIF entries

Use the newly introduced notification chain to send events upon VIF and MFC
addition and deletion. The MFC notifications are sent only on resolved MFC
entries, as unresolved cannot be offloaded.

Signed-off-by: Yotam Gigi <yotamg@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>