iio: imu: st_lsm6dsx: rename st_lsm6dsx_shub_read_reg in st_lsm6dsx_shub_read_output

Rename st_lsm6dsx_shub_read_reg routine in st_lsm6dsx_shub_read_output
since it is used to read from sensorhub channel0 output register

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>