IB/mlx5: Change logic for dispatching IB events for port state

The old logic ignored link state. This led to missing IB events like
when link goes down on the switch while admin state is up or to redundant
events like when admin state goes up while link is down.
To fix that, probe the port state on NETDEV events and compare to last
known state to decide if IB events needs to be dispatched.

FIxes: 5ec8c83e ("IB/mlx5: Port events in RoCE now rely on netdev events")
Signed-off-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Noa Osherovich <noaos@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>