arm64: dts: rockchip: Drop regulator-init-microvolt from two boards

arm64: dts: rockchip: Drop regulator-init-microvolt from two boards

rk3568-roc-pc and rk3588-toybrick-x0 re-introduced this property despite
previous patches removing older instances already.

regulator-init-microvolt is not part of any regulator binding and is
only used in the Rockchip vendor kernel. So drop it.

It is used by u-boot in some places to setup initial regulator-state,
but that should happen in the existing -u-boot devicetree additions.

Fixes: 007b4bb47f44 ("arm64: dts: rockchip: add dts for Firefly Station P2 aka rk3568-roc-pc")
Cc: Furkan Kardame <f.kardame@manjaro.org>
Fixes: 8ffe365f8dc7 ("arm64: dts: rockchip: Add devicetree support for TB-RK3588X board")
Cc: Elon Zhang <zhangzj@rock-chips.com>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20241008203940.2573684-3-heiko@sntech.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>