arm64: dts: allwinner: a100: Add device node for DMA controller

The A100 SoC has a DMA controller that supports 8 DMA channels
to and from various peripherals.

Add a device node for it.

Signed-off-by: Yangtao Li <frank@allwinnertech.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20220830020824.62288-3-samuel@sholland.org