spi: atcspi200: avoid NULL dereference

For SPI_XFER_BEGIN | SPI_XFER_END the code sets data_out = NULL.
In the debug statement we should not dereference this value.
As we do not transfer any data the debug statement is not needed in this
case anyway.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Jagan Teki <jagan@openedev.com>

drivers/spi/atcspi200_spi.c

@@ -229,8 +229,10 @@ static int __atcspi200_spi_xfer(struct nds_spi_slave *ns,
 			__atcspi200_spi_start(ns);
 			break;
 		}
-		debug("spi_xfer: data_out %08X(%p) data_in %08X(%p) data_len %u\n",
-		      *(uint *)data_out, data_out, *(uint *)data_in, data_in, data_len);
+		if (data_out)
+			debug("spi_xfer: data_out %08X(%p) data_in %08X(%p) data_len %u\n",
+			      *(uint *)data_out, data_out, *(uint *)data_in,
+			      data_in, data_len);
 		num_chunks = DIV_ROUND_UP(data_len, max_tran_len);
 		din = data_in;
 		dout = data_out;