efl_ui_tab_pager : Fix type mismatch for calloc

efl_ui_tab_pager : Fix type mismatch for calloc

Summary:
Fix type mismatch.
The return value of function 'calloc' is cast to type 'App_Data *',
which doesn't match the sizeof expression 'sizeof (ad)' passed as its 2nd argument 'sizeof (ad)'.
The size of the result is 8 bytes, value of the sizeof expression is 4.

Test Plan: N/A

Reviewers: bowonryu, SanghyeonLee

Reviewed By: bowonryu, SanghyeonLee

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7067

Change-Id: I2bd5cc58056c97c288e1bfbab93705568ba2b5f4