arm64: dts: Add nodes for pdma0 and pdma1 for exynos7

This patch adds device tree nodes for pdma0 and pdma1 controllers
found on exynos7 SoCs.

Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>