iio: accel: stk8312: Fix buffer alignment in iio_push_to_buffers_with_timestamp()

To make code more readable, use a structure to express the channel
layout and ensure the timestamp is 8 byte aligned.

Found during an audit of all calls of this function.

Fixes: 95c12bba ("iio: accel: Add buffer mode for Sensortek STK8312")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210501170121.512209-7-jic23@kernel.org

drivers/iio/accel/stk8312.c

@@ -102,7 +102,11 @@ struct stk8312_data {
 	u8 mode;
 	struct iio_trigger *dready_trig;
 	bool dready_trigger_on;
-	s8 buffer[16]; /* 3x8-bit channels + 5x8 padding + 64-bit timestamp */
+	/* Ensure timestamp is naturally aligned */
+	struct {
+		s8 chans[3];
+		s64 timestamp __aligned(8);
+	} scan;
 };
 
 static IIO_CONST_ATTR(in_accel_scale_available, STK8312_SCALE_AVAIL);
@@ -437,7 +441,7 @@ static irqreturn_t stk8312_trigger_handler(int irq, void *p)
 		ret = i2c_smbus_read_i2c_block_data(data->client,
 						    STK8312_REG_XOUT,
 						    STK8312_ALL_CHANNEL_SIZE,
-						    data->buffer);
+						    data->scan.chans);
 		if (ret < STK8312_ALL_CHANNEL_SIZE) {
 			dev_err(&data->client->dev, "register read failed\n");
 			mutex_unlock(&data->lock);
@@ -451,12 +455,12 @@ static irqreturn_t stk8312_trigger_handler(int irq, void *p)
 				mutex_unlock(&data->lock);
 				goto err;
 			}
-			data->buffer[i++] = ret;
+			data->scan.chans[i++] = ret;
 		}
 	}
 	mutex_unlock(&data->lock);
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
 					   pf->timestamp);
 err:
 	iio_trigger_notify_done(indio_dev->trig);