ARM: sun5i: dt: Add nodes to represent the DMA controllers

The A10S and A13 SoCs have sun4i-compatible DMA controllers. Let's add
the corresponding nodes to represent them on the device tree.

Signed-off-by: Emilio López <emilio@elopez.com.ar>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>