ARM: dts: Add DMA controller node info on Exynos5420

This patch adds dma controller node info on Exynos5420.
Exynos5420 has adma for audio IPs. As adma clk is dependent
on audss clk provider that will be added later.

Signed-off-by: Padmavathi Venna <padma.v@samsung.com>
Signed-off-by: Leela Krishna Amudala <l.krishna@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>