staging:iio:accel:lis3l02dq make threshold interrupt threaded.

We have moved the timestamp acquisition into the bottom half. It may
technically be less accurate but for this device I very much doubt
anyone cares!

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>