efl_ui_widget: do not eval all the children twice
eval all children is ending up in the complete discovery of the whole
subtree, which is unnessesary here, as we are already discovering the
whole subtree with the calls, these changes are in, so simple
evalulating this is enough.
Depends on D11551
Reviewed By: zmike
Differential Revision: https://phab.enlightenment.org/D11554