dt-bindings: dmaengine: Add JZ4775 bindings.

Add the dmaengine bindings for the JZ4775 SoC from Ingenic.

Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201107122016.89859-2-zhouyanjie@wanyeetech.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>