iio: adc: vf610: 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 uses of
iio_push_to_buffers_with_timestamp()

Fixes: 0010d6b4 ("iio: adc: vf610: Add IIO buffer support for Vybrid ADC")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Stefan-Gabriel Mirea <stefan-gabriel.mirea@nxp.com>
Cc: Sanchayan Maity <maitysanchayan@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210501170121.512209-10-jic23@kernel.org

drivers/iio/adc/vf610_adc.c

@@ -167,7 +167,11 @@ struct vf610_adc {
 	u32 sample_freq_avail[5];
 
 	struct completion completion;
-	u16 buffer[8];
+	/* Ensure the timestamp is naturally aligned */
+	struct {
+		u16 chan;
+		s64 timestamp __aligned(8);
+	} scan;
 };
 
 static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
@@ -579,9 +583,9 @@ static irqreturn_t vf610_adc_isr(int irq, void *dev_id)
 	if (coco & VF610_ADC_HS_COCO0) {
 		info->value = vf610_adc_read_data(info);
 		if (iio_buffer_enabled(indio_dev)) {
-			info->buffer[0] = info->value;
+			info->scan.chan = info->value;
 			iio_push_to_buffers_with_timestamp(indio_dev,
-					info->buffer,
+					&info->scan,
 					iio_get_time_ns(indio_dev));
 			iio_trigger_notify_done(indio_dev->trig);
 		} else