arm64: dts: allwinner: pinebook: Fix 5v0 boost regulator

Now that AXP803 GPIO support is available, we can properly model
the hardware. Replace the use of GPIO0-LDO with a fixed regulator
controlled by GPIO0. This boost regulator is used to power the
(internal and external) USB ports, as well as the speakers.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>