efl_ui_selection_manager: fix potential out of bounce access

efl_ui_selection_manager: fix potential out of bounce access

Summary:
We have been casting the selection to unsigned char * for the address of
sel and not for the value. Coverity pointed this out:
Overrunning buffer pointed to by (unsigned char *)&sel of 8 bytes by
passing it to a function which accesses it at byte offset 167 using argument 168

It seems this has been working by memory layout and luck if I understand
it all correctly.

Coverity ID: 1402666

Reviewers: thiepha, raster, zmike

Reviewed By: zmike

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D10107