dmaengine: sun6i: allow build on ARM64 platforms (sun50i)

As 64-bit Allwinner H5 SoC has the same DMA engine with H3, the DMA
driver should be allowed to be built for ARM64, in order to make it work on H5.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>