Add KF5::WaylandServer to include the required directories

Summary: abstract_egl_backend.cpp includes several kwayland headers, but the include paths aren't added for kwayland. This patch solves the problem, by adding kwayland as requirement for the opengl scene plugin.

Reviewers: KWin, graesslin

Reviewed By: KWin, graesslin

Subscribers: kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D10373