arm64: dts: rockchip: fix audio-supply for Rock Pi 4

arm64: dts: rockchip: fix audio-supply for Rock Pi 4

As stated in the schematics [1] and [2] P5 the APIO5 domain is supplied
by RK808-D Buck4, which in our case vcc1v8_codec - i.e. a 1.8 V regulator.

Currently only white noise comes from the ES8316's output, which - for
whatever reason - came up only after the the correct switch from i2s0_8ch_bus
to i2s0_2ch_bus for i2s0's pinctrl was done.

Fix this by setting the correct regulator for audio-supply.

[1] https://dl.radxa.com/rockpi4/docs/hw/rockpi4/rockpi4_v13_sch_20181112.pdf
[2] https://dl.radxa.com/rockpi4/docs/hw/rockpi4/rockpi_4c_v12_sch_20200620.pdf

Fixes: 1b5715c602fd ("arm64: dts: rockchip: add ROCK Pi 4 DTS support")
Signed-off-by: Alex Bee <knaerzche@gmail.com>
Link: https://lore.kernel.org/r/20211027143726.165809-1-knaerzche@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>