dmaengine: Introduce DW AXI DMAC driver

This patch adds support for the DW AXI DMAC controller.
DW AXI DMAC is a part of HSDK development board from Synopsys.

In this driver implementation only DMA_MEMCPY transfers are
supported.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>