net: bcmgenet: Remove phy_stop() from bcmgenet_netif_stop()

The call to phy_stop() races with the later call to phy_disconnect(),
resulting in concurrent phy_suspend() calls being run from different
CPUs. The final call to phy_disconnect() ensures that the PHY is
stopped and suspended, too.

Fixes: c96e731c ("net: bcmgenet: connect and disconnect from the PHY state machine")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>