Add cluster regulator supply properties as a preparation to
adding generic cpufreq-dt driver support for Exynos542x and
Exynos5800 based boards.

Cc: Doug Anderson <dianders@chromium.org>
Cc: Javier Martinez Canillas <javier@osg.samsung.com>
Cc: Andreas Faerber <afaerber@suse.de>
Cc: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>