iio: imu: st_lsm6dsx: introduce st_lsm6dsx_device_set_enable routine

Introduce st_lsm6dsx_device_set_enable utility routine and remove
duplicated code used to enable/disable sensors

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/e3fbe5d4a3bed41130908669f745f78c8505cf47.1665399959.git.lorenzo@kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>