Move the board-specific phy initialization from early boot into ifup phase. The
board specific phy initialization may need to implement delays, or bus
communication, for example via i2c bus.
These OS services are not necessarily available yet in arm64_netinitialize, and
PHY initialization is not necessary until the driver actually starts using it.
In addition, this allows the board to reset the ethernet phy at every ifup,
if needed for error recover.
Signed-off-by: Jukka Laitinen <jukka.laitinen@tii.ae>