iio: light: si1133: Use get_unaligned_be24()

This makes the driver code slightly easier to read.

Cc: Maxime Roussin-Bélanger <maxime.roussinbelanger@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/si1133.c

@@ -17,6 +17,8 @@
 
 #include <linux/util_macros.h>
 
+#include <asm/unaligned.h>
+
 #define SI1133_REG_PART_ID		0x00
 #define SI1133_REG_REV_ID		0x01
 #define SI1133_REG_MFR_ID		0x02
@@ -104,8 +106,6 @@
 #define SI1133_LUX_BUFFER_SIZE		9
 #define SI1133_MEASURE_BUFFER_SIZE	3
 
-#define SI1133_SIGN_BIT_INDEX 23
-
 static const int si1133_scale_available[] = {
 	1, 2, 4, 8, 16, 32, 64, 128};
 
@@ -633,8 +633,7 @@ static int si1133_measure(struct si1133_data *data,
 	if (err)
 		return err;
 
-	*val = sign_extend32((buffer[0] << 16) | (buffer[1] << 8) | buffer[2],
-			     SI1133_SIGN_BIT_INDEX);
+	*val = sign_extend32(get_unaligned_be24(&buffer[0]), 23);
 
 	return err;
 }
@@ -723,16 +722,11 @@ static int si1133_get_lux(struct si1133_data *data, int *val)
 	if (err)
 		return err;
 
-	high_vis =
-		sign_extend32((buffer[0] << 16) | (buffer[1] << 8) | buffer[2],
-			      SI1133_SIGN_BIT_INDEX);
+	high_vis = sign_extend32(get_unaligned_be24(&buffer[0]), 23);
 
-	low_vis =
-		sign_extend32((buffer[3] << 16) | (buffer[4] << 8) | buffer[5],
-			      SI1133_SIGN_BIT_INDEX);
+	low_vis = sign_extend32(get_unaligned_be24(&buffer[3]), 23);
 
-	ir = sign_extend32((buffer[6] << 16) | (buffer[7] << 8) | buffer[8],
-			   SI1133_SIGN_BIT_INDEX);
+	ir = sign_extend32(get_unaligned_be24(&buffer[6]), 23);
 
 	if (high_vis > SI1133_ADC_THRESHOLD || ir > SI1133_ADC_THRESHOLD)
 		lux = si1133_calc_polynomial(high_vis, ir,