elm_interface_scrollable: fix wanted coordinate calculation

elm_interface_scrollable: fix wanted coordinate calculation

Summary:
boundary check of _elm_scroll_wanted_coordinates_update() is wrong.
boundary was checked with assumption that 0, 0 is top, left
however, 0, 0 could be different according to usages, in case of gengrid, 0, 0 was center left not top left)

Do not assume the min/max value, but use pan min/max value for boundary check

Fixes T1092

Test Plan: elementary_test -> grid -> uncheck multi select mode -> select first item -> click bring in -> resize window

Reviewers: raster, woohyun, seoz, zmike

CC: seoz
Maniphest Tasks: T1092

Differential Revision: https://phab.enlightenment.org/D720