iio: adc: ads124: avoid buffer overflow

When initializing the priv->data array starting from index 1, there is one
less element to consider than when initializing the full array.

Fixes: e717f8c ("iio: adc: Add the TI ads124s08 ADC code")
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Reviewed-by: Dan Murphy <dmurphy@ti.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ti-ads124s08.c

@@ -202,7 +202,7 @@ static int ads124s_read(struct iio_dev *indio_dev, unsigned int chan)
 	};
 
 	priv->data[0] = ADS124S08_CMD_RDATA;
-	memset(&priv->data[1], ADS124S08_CMD_NOP, sizeof(priv->data));
+	memset(&priv->data[1], ADS124S08_CMD_NOP, sizeof(priv->data) - 1);
 
 	ret = spi_sync_transfer(priv->spi, t, ARRAY_SIZE(t));
 	if (ret < 0)