Input: elantech - demote obvious abuse of kernel-doc header

Input: elantech - demote obvious abuse of kernel-doc header

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

 drivers/input/mouse/elantech.c:1837: warning: Function parameter or member 'psmouse' not described in 'elantech_setup_smbus'
 drivers/input/mouse/elantech.c:1837: warning: Function parameter or member 'info' not described in 'elantech_setup_smbus'
 drivers/input/mouse/elantech.c:1837: warning: Function parameter or member 'leave_breadcrumbs' not described in 'elantech_setup_smbus'

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104162427.2984742-13-lee.jones@linaro.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>