popup: remove max_sc_w because it's duplicate job

popup: remove max_sc_w because it's duplicate job

Summary:
max_sc_w decide popup's "content" area size when popup scrollable is TRUE.
but in popup's edc, "elm/popup/content/XXXX" has min size when scrollable is TRUE. (and it is content area layout)
max_sc_w has fixed value, so I think deciding by edc is better than fixed code.

Test Plan:
1. elementary_test -to popup
2. check "Enable popup scroll"
3. click any list item.
4. observe popup and compare before this patch.

Reviewers: singh.amitesh, herb, Hermet, raster

Subscribers: cedric, jpeg

Differential Revision: https://phab.enlightenment.org/D4113