iio: light: apds9960: correct FIFO check condition

Correct issue that the last entry in FIFO was being read twice due
to an incorrect decrement of entry count variable before condition
check.
Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/apds9960.c

@@ -769,7 +769,7 @@ static void apds9960_read_gesture_fifo(struct apds9960_data *data)
 	mutex_lock(&data->lock);
 	data->gesture_mode_running = 1;
 
-	while (cnt-- || (cnt = apds9660_fifo_is_empty(data) > 0)) {
+	while (cnt || (cnt = apds9660_fifo_is_empty(data) > 0)) {
 		ret = regmap_bulk_read(data->regmap, APDS9960_REG_GFIFO_BASE,
 				      &data->buffer, 4);
 
@@ -777,6 +777,7 @@ static void apds9960_read_gesture_fifo(struct apds9960_data *data)
 			goto err_read;
 
 		iio_push_to_buffers(data->indio_dev, data->buffer);
+		cnt--;
 	}
 
 err_read: