arm64: dts: rockchip: Drop rockchip prefix of s-p-c PMIC prop from px30

arm64: dts: rockchip: Drop rockchip prefix of s-p-c PMIC prop from px30

Property 'rockchip,system-power-controller' was deprecated in commit
961748bb1555 ("dt-bindings: mfd: rk8xx: Deprecate rockchip,system-power-controller")

in the "rockchip,rk{805,808,809,817,818}.yaml" mtd bindings and its
replacement is (just) 'system-power-controller'.

Update the px30 DT files which still used the deprecated variant.

Signed-off-by: Diederik de Haas <didi.debian@cknow.org>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/20241008105450.20648-2-didi.debian@cknow.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>