dmaengine: vdma: Add support for cyclic dma mode

This patch adds support for AXI DMA cyclic dma mode.
In cyclic mode, DMA fetches and processes the same
BDs without interruption. The DMA continues to fetch and process
until it is stopped or reset.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>