iio: adc: hx711: 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: d3bf60450d47 ("iio: hx711: add triggered buffer support")
Signed-off-by: Jonathan Cameron <[e-mail]>
Cc: Andreas Klinger <[e-mail]>
Reviewed-by: Nuno Sá <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iio/adc/hx711.c

···
 	struct mutex		lock;
 	/*
 	 * triggered buffer
-	 * 2x32-bit channel + 64-bit timestamp
+	 * 2x32-bit channel + 64-bit naturally aligned timestamp
 	 */
-	u32			buffer[4];
+	u32			buffer[4] __aligned(8);
 	/*
 	 * delay after a rising edge on SCK until the data is ready DOUT
 	 * this is dependent on the hx711 where the datasheet tells a