efl_ui_win: fix hw accel detection

efl_ui_win: fix hw accel detection

the ordering of priority here is supposed to be:

1. env vars
2. global override config
3. window config
4. global config

in the case where 1 and 3 were not set, however, this would end up
mangling the global config values and not using the gl options

@fix

Reviewed-by: Cedric BAIL <cedric.bail@free.fr>
Differential Revision: https://phab.enlightenment.org/D8389