iio: gyro: adxrs290: Add triggered buffer support

Provide a way for continuous data capture by setting up buffer support. The
data ready signal exposed at the SYNC pin of the ADXRS290 is exploited as
a hardware interrupt which triggers to fill the buffer.

Triggered buffer setup was tested with both hardware trigger (DATA_RDY) and
software triggers (sysfs-trig & hrtimer).

Signed-off-by: Nishant Malpani <nish.malpani25@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200910180450.29696-2-nish.malpani25@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>