iio: imu: st_lsm6dsx: check return value from st_lsm6dsx_sensor_set_enable

Add missing return value check in st_lsm6dsx_read_oneshot disabling the
sensor. The issue is reported by coverity with the following error:

Unchecked return value:
If the function returns an error value, the error value may be mistaken
for a normal value.

Addresses-Coverity-ID: 1446733 ("Unchecked return value")
Fixes: b5969abf ("iio: imu: st_lsm6dsx: add motion events")
Fixes: 290a6ce1 ("iio: imu: add support to lsm6dsx driver")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>