iio: imu: st_lsm6dsx: st_lsm6dsx_shub: Demote obvious misuse of kerneldoc to standard comment blocks

No attempt has been made to document any of the demoted functions here.

Fixes the following W=1 kernel build warning(s):

 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:174: warning: Function parameter or member 'hw' not described in 'st_lsm6dsx_shub_read_output'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:174: warning: Function parameter or member 'data' not described in 'st_lsm6dsx_shub_read_output'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:174: warning: Function parameter or member 'len' not described in 'st_lsm6dsx_shub_read_output'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:205: warning: Function parameter or member 'hw' not described in 'st_lsm6dsx_shub_write_reg'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:205: warning: Function parameter or member 'addr' not described in 'st_lsm6dsx_shub_write_reg'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:205: warning: Function parameter or member 'data' not described in 'st_lsm6dsx_shub_write_reg'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:205: warning: Function parameter or member 'len' not described in 'st_lsm6dsx_shub_write_reg'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:285: warning: Function parameter or member 'sensor' not described in 'st_lsm6dsx_shub_read'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:285: warning: Function parameter or member 'addr' not described in 'st_lsm6dsx_shub_read'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:285: warning: Function parameter or member 'data' not described in 'st_lsm6dsx_shub_read'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:285: warning: Function parameter or member 'len' not described in 'st_lsm6dsx_shub_read'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:335: warning: Function parameter or member 'sensor' not described in 'st_lsm6dsx_shub_write'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:335: warning: Function parameter or member 'addr' not described in 'st_lsm6dsx_shub_write'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:335: warning: Function parameter or member 'data' not described in 'st_lsm6dsx_shub_write'
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_shub.c:335: warning: Function parameter or member 'len' not described in 'st_lsm6dsx_shub_write'

Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>