dmaengine: xilinx_dma: Print debug message when no free tx segments

The driver should not run out of tx segments in normal operation. But,
if the user attempts to prepare a transaction with a large sg list,
the driver may not have enough free segments to accommodate the request.

Log a message at the debug level to inform the user in case they are
experiencing issues.
Signed-off-by: Nicholas Graumann <nick.graumann@gmail.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Link: https://lore.kernel.org/r/1571150904-3988-7-git-send-email-radhey.shyam.pandey@xilinx.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/xilinx/xilinx_dma.c

@@ -612,6 +612,9 @@ xilinx_axidma_alloc_tx_segment(struct xilinx_dma_chan *chan)
 	}
 	spin_unlock_irqrestore(&chan->lock, flags);
 
+	if (!segment)
+		dev_dbg(chan->dev, "Could not find free tx segment\n");
+
 	return segment;
 }