display: misc: Relocate stay_touchscreen_off getter and setter

display: misc: Relocate stay_touchscreen_off getter and setter

Remove and redefine set_stay_touchscreen_off() to reduce plugin duplication

These functions are added to below display-touchscreen.
void display_misc_set_stay_touchscreen_off(bool on)
-> This function sets stay_touchscreen_off variable
void display_misc_get_stay_touchscreen_off(bool *on)
-> This function gets stay_touchscreen_off value

Change-Id: I09df7229111442affab75c43e70ae2038f82c966
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>