IB/mlx5: Port events in RoCE now rely on netdev events

Since ib_query_port() in RoCE returns the state of its netdev as the port
state, it makes sense to propagate the port up/down events to ib_core
when the netdev port state changes, instead of relying on traditional
core events.

This also keeps both the event and ib_query_port() synchronized.

Signed-off-by: Aviv Heller <avivh@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>