sunxi: Pine-H64: Explicitly enable PHY regulator

sunxi: Pine-H64: Explicitly enable PHY regulator

According to the devicetree and the schematic, the 3.3V power rail for
the PHY is enabled by GPIO PC16. It's wired as active-high, with a
pull-up resistor, so actually works already when the GPIO is in
High-Z state.

However we should not take any chances and explicitly set the GPIO pin
to high, to avoid accidentally losing the PHY power.
The existing MACPWR Kconfig allows to do this easily.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Amit Singh Tomar <amittomer25@gmail.com> # Pine64+
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>