net: mvpp2: improve the link management function

When the link status changes, the phylib calls the link_event function
in the mvpp2 driver. Before this patch only the egress/ingress transmit
was enabled/disabled. This patch adds more functionality to the link
status management code by enabling/disabling the port per-cpu
interrupts, and the port itself. The queues are now stopped as well, and
the netif carrier helpers are called.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>