display: Move image effect functions from plugins to core display module

display: Move image effect functions from plugins to core display module

Remove and redefine functions related to display image effect.
These functions are added below display-panel.

int display_panel_set_image_effect(enum display_image_effect effect);
int display_panel_get_image_effect(enum display_image_effect *effect);
-> With display_image_effect enum type, it is possible to get and set image effect type.

Change-Id: I479aa296053ef75b18b4e4b2c3f93e40ecc03191
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>