iio: adc: ti-adc0832: Fix alignment for DMA safety

____cacheline_aligned is an insufficient guarantee for non-coherent DMA
on platforms with 128 byte cachelines above L1.  Switch to the updated
IIO_DMA_MINALIGN definition.

Fixes: efc945fb ("iio: adc: add support for ADC0831/ADC0832/ADC0834/ADC0838 chips")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220508175712.647246-29-jic23@kernel.org