iio: accel: bma400: Add step change event

Added support for event when there is a detection of step change.
INT1 pin is used to interrupt and event is pushed to userspace.

Signed-off-by: Jagath Jog J <jagathjog1996@gmail.com>
Link: https://lore.kernel.org/r/20220505133021.22362-7-jagathjog1996@gmail.com


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