net: phy: make of_set_phy_supported work with genphy driver

of_set_phy_supported allows overwiting hardware capabilities of
a phy with values from the devicetree. of_set_phy_supported is
called right after phy_device_register in the assumption that
phy_probe is called from phy_device_register and the features
of the phy are already initialized. For the genphy driver this
is not true, here phy_probe is called later during phy_connect
time. phy_probe will then overwrite all settings done from
of_set_phy_supported
Fix this by moving of_set_phy_supported to the core phy code
and calling it from phy_probe.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>