Fix brightness shortcuts in the whitelist

Summary: Since D9053, screen and keyboard brightness shortcuts are sent from powerdevil's component instead of kded's, so the brightness adjusting from locked screen has been broken.

Test Plan: Brightness adjusting should work when the screen is locked.

Reviewers: Plasma, davidedmundson

Reviewed By: Plasma, davidedmundson

Subscribers: graesslin, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D10065