[EFL] Remove duplicated compiler flag
https://bugs.webkit.org/show_bug.cgi?id=133838

Reviewed by Anders Carlsson.

In r169798, literal-suffix was added for EFL port in order to fix build break. However,
it added to common compiler options. So, it is duplicated.

* Source/cmake/WebKitHelpers.cmake:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@169967 268f45cc-cd09-0410-ab3c-d52691b4dbfc