dma: Add Xilinx AXI Video Direct Memory Access Engine driver support

This is the driver for the AXI Video Direct Memory Access (AXI
VDMA) core, which is a soft Xilinx IP core that provides high-
bandwidth direct memory access between memory and AXI4-Stream
type video target peripherals. The core provides efficient two
dimensional DMA operations with independent asynchronous read
and write channel operation.

This module works on Zynq (ARM Based SoC) and Microblaze platforms.

Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Reviewed-by: Levente Kurusa <levex@linux.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>