Staging: iio: Fix sparse endian warning

Fix following sparse warning:
warning: cast to restricted __be16
Signed-off-by: NKsenija Stanojevic <ksenija.stanojevic@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/adc/ad7606_spi.c

@@ -21,7 +21,8 @@ static int ad7606_spi_read_block(struct device *dev,
 {
 	struct spi_device *spi = to_spi_device(dev);
 	int i, ret;
-	unsigned short *data = buf;
+	unsigned short *data;
+	__be16 *bdata = buf;
 
 	ret = spi_read(spi, buf, count * 2);
 	if (ret < 0) {
@@ -30,7 +31,7 @@ static int ad7606_spi_read_block(struct device *dev,
 	}
 
 	for (i = 0; i < count; i++)
-		data[i] = be16_to_cpu(data[i]);
+		data[i] = be16_to_cpu(bdata[i]);
 
 	return 0;
 }