dt-bindings: jz4780-dma: Update bindings to reflect driver changes

The driver now expects the devicetree to supply a second memory
resource. This resource is mandatory on the newly supported SoCs.
For the JZ4780, new devicetree code must also provide it, although the
driver is still compatible with older devicetree binaries.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>