multibuttonentry : fix box indicated item correctly in item_insert_before and item_insert_after
Summary:
If user added item with item_insert_before and item_insert_after, item was not displayed.
For this reason, fixed box indicated item correctly from reference->button to VIEW(reference).
Additionally, remove the unused variable button in _Multibuttonentry_Item struct.
Reviewers: woohyun, CHAN, cedric, jpeg
Reviewed By: CHAN, jpeg
Subscribers: cedric, jpeg
Differential Revision: https://phab.enlightenment.org/D4708
Change-Id: Idbc0867bec31e25e6622fe6e7967c774513f860d
Signed-off-by: JEONGHYUN YUN <jh0506.yun@samsung.com>