dt-bindings: arm: samsung: pmu: Add missing properties

dt-bindings: arm: samsung: pmu: Add missing properties

Add common properties appearing in DTSes (assigned-clock-parents,
assigned-clocks) to fix dtbs_check warnings like:

  arch/arm64/boot/dts/exynos/exynos5433-tm2.dt.yaml: system-controller@105c0000:
    'assigned-clock-parents', 'assigned-clocks' do not match any of the regexes: 'pinctrl-[0-9]+'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200903191311.12293-1-krzk@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>