display: misc: Relocate battery_health_changed() to reduce plugin duplication

display: misc: Relocate battery_health_changed() to reduce plugin duplication

Remove and redefine battery_health_changed() in plugins/display/core.c
-> This function sets battery/dimstay flag and it is called from battery module.

This function is added to below display-misc.
void display_misc_register_battery_health_notifier(void)
void display_misc_unregister_battery_health_notifier(void)
-> register/unregister notifier is added for above notifier callback.

During display plugins refactoriung, this function will be relocated.

Change-Id: Ib48187458ebfdf0e279c5ea373f401260eb1e597
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>