net: aquantia: Fixed transient link up/down/up notification

When doing ifconfig down/up, driver did not reported carrier_off neither
in nic_stop nor in nic_start. That caused link to be visible as "up"
during couple of seconds immediately after "ifconfig up".

Signed-off-by: Pavel Belous <pavel.belous@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>