ARM: sunxi: Add EMAC Controller to Hackberry dt

The Hackberry has a PHY that needs to be powered up through a GPIO, so
we need to use a fixed regulator here.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Tested-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>