sysutils/consolekit2: enable drm/evdev, fix drm device recognition

This makes it possible to launch a Wayland compositor using ConsoleKit2 as the
session controller.

Submitted by: greg@unrelenting.technology
Obtained from: https://github.com/DankBSD/ports/commits/lite/sysutils/consolekit2
Differential Revision: https://reviews.freebsd.org/D18754