iio: imu: st_lsm6dsx: rely on st_lsm6dsx_update_bits_locked configuring events

Rely on st_lsm6dsx_update_bits_locked in st_lsm6dsx_write_event and
st_lsm6dsx_event_setup routines since they can run concurrently with
sensor hub configuration

Fixes: b5969abf ("iio: imu: st_lsm6dsx: add motion events")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>