elm_segment_control: fix invalid parameter
elm_segment_control: fix invalid parameter

Summary:
Eo complained about an invalid type 'Edje_Object' passed to
elm_widget_sub_object_add(). It is the segment control itself
that should be the subject of the call to this function.

@fix

Test Plan: elementary_test: no more Eo errors

Reviewers: cedric, stefan_schmidt

Differential Revision: https://phab.enlightenment.org/D3277

rvandegrift/elementary,tasn/elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary