display: Relocate display_on/off_by_reason()

display: Relocate display_on/off_by_reason()

display_on/off_by_reason() is used by dbus_changestatebyreason call.
1. Set display on/off reason to the flag.
2. Check if it is possible to go to lcd_on/off procedure.
   If possible, go to the lcd on/off procedure.
3. After that, update current, before display state and do action about S_NORMAL/S_LCDOFF.

For relocating these, the string of device operation declaration has also been moved to shared/devices.h
There is no reason for the same string to exist in all plugins.

New functions are added below display-panel.
- int display_panel_display_turn_on_by_reason(const char *reason, int timeout);
- int display_panel_display_turn_off_by_reason(const char *reason);
    -> These replace display_on/off_by_reason()

Change-Id: Ia22ee6295fa138c3742be62c3bbc2c357716caf5
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>