display: Move display get dpms state function from plugin to core display module

display: Move display get dpms state function from plugin to core display module

Remove and redefine display dpms state function.
These functions are added to below display-panel.

int display_panel_get_dpms_state(void)
-> This function returns dpms state and replaces get_lcd_power_node located in plugins.
void display_panel_set_dpms_running_state(int val)
-> This function initialize dpms_running_state

Change-Id: I34e29e3477113d2f19835c0782303334ba0d870f
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>