etraxfs_dma: Dont forward zero-length payload to clients

Signed-off-by: NEdgar E. Iglesias <edgar.iglesias@xilinx.com>

hw/dma/etraxfs_dma.c

@@ -440,13 +440,16 @@ static int channel_out_run(struct fs_dma_ctrl *ctrl, int c)
 		D(printf("channel %d pushes %x %u bytes eop=%u\n", c,
 		         saved_data_buf, len, out_eop));
 
-		if (ctrl->channels[c].client->client.push)
+		if (ctrl->channels[c].client->client.push) {
+                        if (len > 0) {
 				ctrl->channels[c].client->client.push(
 					ctrl->channels[c].client->client.opaque,
 					buf, len, out_eop);
-		else
+			}
+		} else {
 			printf("WARNING: DMA ch%d dataloss,"
 			       " no attached client.\n", c);
+		}
 
 		saved_data_buf += len;