dmaengine: xilinx: Use different channel names for each dma
Current driver assumes that child node channel name is either
"xlnx,axi-vdma-mm2s-channel" or "xlnx,axi-vdma-s2mm-channel"
which is confusing the users of AXI DMA and CDMA.
This patch fixes this issue by using different channel
names for the AXI DMA and AXI CDMA child nodes.