dmaengine: vdma: Rename xilinx_vdma_ prefix to xilinx_dma

This patch renames the xilinx_vdma_ prefix to xilinx_dma
for the API's and masks that will be shared b/w three DMA
IP cores.

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