iio: st_sensors: Use get_unaligned_be24() and sign_extend32()

Use these functions instead of open-coding them.

Cc: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/common/st_sensors/st_sensors_core.c

@@ -20,11 +20,6 @@
 
 #include "st_sensors_core.h"
 
-static inline u32 st_sensors_get_unaligned_le24(const u8 *p)
-{
-	return (s32)((p[0] | p[1] << 8 | p[2] << 16) << 8) >> 8;
-}
-
 int st_sensors_write_data_with_mask(struct iio_dev *indio_dev,
 				    u8 reg_addr, u8 mask, u8 data)
 {
@@ -543,7 +538,7 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev,
 	else if (byte_for_channel == 2)
 		*data = (s16)get_unaligned_le16(outdata);
 	else if (byte_for_channel == 3)
-		*data = (s32)st_sensors_get_unaligned_le24(outdata);
+		*data = (s32)sign_extend32(get_unaligned_le24(outdata), 23);
 
 st_sensors_free_memory:
 	kfree(outdata);