dt-bindings: dma: ingenic: Support #dma-cells = <3>

Extend the binding to support specifying a different request type for
each direction.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20211206174259.68133-3-paul@crapouillou.net


Signed-off-by: Vinod Koul <vkoul@kernel.org>