elm_map: Fix to calculate map size not to be smaller than viewport size
elm_map: Fix to calculate map size not to be smaller than viewport size

Summary:
Fix to calculator map size not to be smaller than viewport size when zoom mode is either fit or fill.
Previously, map size could be either smaller or larger than viewport.
@fix

Reviewers: Hermet, raster

Reviewed By: raster

Differential Revision: https://phab.enlightenment.org/D861

rvandegrift/elementary,FlorentRevest/Elementary,tasn/elementary,FlorentRevest/Elementary,rvandegrift/elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary,FlorentRevest/Elementary,tasn/elementary,tasn/elementary,FlorentRevest/Elementary,tasn/elementary