dt-bindings: iommu: Convert Samsung Exynos IOMMU H/W, System MMU to dt-schema

Convert Samsung Exynos IOMMU H/W, System Memory Management Unit
to newer dt-schema format.

Signed-off-by: Maciej Falkowski <m.falkowski@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>