iio: adc: ti-adc161s626: fix buffer read on big-endian

iio: adc: ti-adc161s626: fix buffer read on big-endian

Rework ti_adc_trigger_handler() to properly handle data on big-endian
architectures. The scan data format is 16-bit CPU-endian, so we can't
cast it to a int * on big-endian and expect it to work. Instead, we
introduce a local int variable to read the data into, and then copy it
to the buffer.

Since the buffer isn't passed to any SPI functions, we don't need it to
be DMA-safe. So we can drop it from the driver data struct and just
use stack memory for the scan data.

Since there is only one data value (plus timestamp), we don't need an
array and can just declare a struct with the correct data type instead.

Also fix alignment of iio_get_time_ns() to ( while we are touching this.

Fixes: 4d671b71beef ("iio: adc: ti-adc161s626: add support for TI 1-channel differential ADCs")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>