mfd: rk8xx-core: Check "system-power-controller" first

mfd: rk8xx-core: Check "system-power-controller" first

Commit 961748bb1555 ("dt-bindings: mfd: rk8xx: Deprecate rockchip,system-
power-controller") made the property "rockchip,system-power-controller"
deprecated in favor of the shorter, universal form "system-power-controller".
Following the updates to the board dts files, [1] make the favored property
name checked first, to save a few CPU cycles.

[1] https://lore.kernel.org/linux-rockchip/20241008105450.20648-1-didi.debian@cknow.org/T/#u

Signed-off-by: Dragan Simic <dsimic@manjaro.org>
Link: https://lore.kernel.org/r/08d4e88974c205eba124086ce156622e2e4cdc20.1728397516.git.dsimic@manjaro.org
Signed-off-by: Lee Jones <lee@kernel.org>