iio: accel: bma400: Add activity recognition support

Add support for activity recognition like STILL, WALKING, RUNNING
and these events are pushed to the userspace whenever the STEP
interrupt occurs.

Signed-off-by: Jagath Jog J <jagathjog1996@gmail.com>
Link: https://lore.kernel.org/r/20220505133021.22362-8-jagathjog1996@gmail.com


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