net: axienet: Set mac_managed_pm

The external PHY will undergo a soft reset twice during the resume process
when it wake up from suspend. The first reset occurs when the axienet
driver calls phylink_of_phy_connect(), and the second occurs when
mdio_bus_phy_resume() invokes phy_init_hw(). The second soft reset of the
external PHY does not reinitialize the internal PHY, which causes issues
with the internal PHY, resulting in the PHY link being down. To prevent
this, setting the mac_managed_pm flag skips the mdio_bus_phy_resume()
function.

Fixes: a129b41f ("Revert "net: phy: dp83867: perform soft reset and retain established link"")
Signed-off-by: Nick Hu <nick.hu@sifive.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250217055843.19799-1-nick.hu@sifive.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>