ARM: sun8i: a83t: Add device node for DMA controller

The A83T SoC has a DMA controller that supports 8 DMA channels
to and from various peripherals.

Add a device node for it.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>