efl_ui_panes: fix not to consider content min size for legacy panes
Summary:
Since legacy panes did not consider its content's min size, the
content's min size calculation logic is not done for legacy panes.
Reviewers: zmike
Reviewed By: zmike
Subscribers: cedric, reviewers, committers
Tags: efl
Differential Revision: https://phab.enlightenment.org/D10372