iio: imu: st_lsm6dsx: check return value from st_lsm6dsx_sensor_set_enable

Add missing return value check in st_lsm6dsx_shub_read_oneshot disabling
the slave device connected to the st_lsm6dsx i2c controller.
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: 1456767 ("Unchecked return value")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>