arm64: dts: allwinner: a64: NanoPi-A64: Fix DCDC1 voltage

According to the NanoPi-A64 schematics, DCDC1 is connected to a voltage
rail named "VDD_SYS_3.3V". All users seem to expect 3.3V here: the
Ethernet PHY, the uSD card slot, the camera interface and the GPIO pins
on the headers.
Fix up the voltage on the regulator to lift it up to 3.3V.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>