dmaengine: dma-jz4780: Add support for the JZ4740 SoC

The JZ4740 SoC has a single DMA core starring six DMA channels.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>