arm64: dts: allwinner: pinephone: Set ALDO3 to exactly 3v0

ALDO3 is used as the power supply for the LRADC keys voltage divider,
in addition to supplying AVCC and VCC-PLL. While AVCC and VCC-PLL will
accept any voltage between 2v7 and 3v3, LRADC needs a precise 3v0 input
to maintain the expected 2:3 ratio between the internal 2v0 reference
voltage and the external supply.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20201105054135.24860-3-samuel@sholland.org