iio: accel: bma220: 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: 194dc4c714 ("iio: accel: Add triggered buffer support for BMA220")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210501170121.512209-3-jic23@kernel.org

drivers/iio/accel/bma220_spi.c

@@ -63,7 +63,11 @@ static const int bma220_scale_table[][2] = {
 struct bma220_data {
 	struct spi_device *spi_device;
 	struct mutex lock;
-	s8 buffer[16]; /* 3x8-bit channels + 5x8 padding + 8x8 timestamp */
+	struct {
+		s8 chans[3];
+		/* Ensure timestamp is naturally aligned. */
+		s64 timestamp __aligned(8);
+	} scan;
 	u8 tx_buf[2] ____cacheline_aligned;
 };
 
@@ -94,12 +98,12 @@ static irqreturn_t bma220_trigger_handler(int irq, void *p)
 
 	mutex_lock(&data->lock);
 	data->tx_buf[0] = BMA220_REG_ACCEL_X | BMA220_READ_MASK;
-	ret = spi_write_then_read(spi, data->tx_buf, 1, data->buffer,
+	ret = spi_write_then_read(spi, data->tx_buf, 1, &data->scan.chans,
 				  ARRAY_SIZE(bma220_channels) - 1);
 	if (ret < 0)
 		goto err;
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
 					   pf->timestamp);
 err:
 	mutex_unlock(&data->lock);