ARM: dts: exynos: Add mem-2-mem Scaler devices

There are 3 scaler devices in Exynos5420 SoCs, all are a part of MSCL
power domain. MSCL power domain and SYSMMU controllers (two per each
scaler device) have been already added to exynos5420.dtsi earlier,
so bind them to newly added devices.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>