[libkwineffects] Detect modern Radeon GPUs

Summary:
Currently, KWin is not able to detect Radeon GPUs with GCN architecture.
This patch tries to address that.

Reviewers: #kwin, graesslin

Reviewed By: #kwin, graesslin

Subscribers: graesslin, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D17715