net: bcmasp: Indicate MAC is in charge of PHY PM

Avoid the PHY library call unnecessarily into the suspend/resume
functions by setting phydev->mac_managed_pm to true. The ASP driver
essentially does exactly what mdio_bus_phy_resume() does.

Fixes: 490cb412

 ("net: bcmasp: Add support for ASP2.0 Ethernet controller")
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Justin Chen <justin.chen@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>