dmaengine: jz4780: add driver for the Ingenic JZ4780 DMA controller

This patch adds a driver for the DMA controller found in the Ingenic
JZ4780.

It currently does not implement any support for the programmable firmware
feature of the controller - this is not necessary for most uses. It also
does not take priority into account when allocating channels, it just
allocates the first available channel. This can be implemented later.

Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
[Updated for dmaengine api changes, Add residue support, couple of minor fixes]
Signed-off-by: Vinod Koul <vinod.koul@intel.com>