arm64: dts: rockchip: mark system power controller and fix typo on orangepi-5-plus

Mark the PMIC as system power controller, so the board will shut-down
properly and fix the typo on rk806_dvs1_null pins property.

Fixes: 236d225e

 ("arm64: dts: rockchip: Add board device tree for rk3588-orangepi-5-plus")
Signed-off-by: Muhammed Efe Cetin <efectn@protonmail.com>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/20240407173210.372585-1-efectn@6tel.net
Signed-off-by: Heiko Stuebner <heiko@sntech.de>