dmaengine: sun6i: Add support for Allwinner A64 and compatibles

The A64 SoC has the same dma engine as the H3 (sun8i), with a
reduced amount of physical channels. To allow future reuse of the
compatible, leave the channel count etc. in the config data blank
and retrieve it from the devicetree.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>