Before this commit we were trying to add most drm devices twice, once
from xf86platformProbe() and once from config_udev_init().
This results in somewhat confusing messages in Xorg.log, ie:
(II) xfree86: Adding drm device (/dev/dri/card0)
Later followed by:
(II) config/udev: Adding drm device (/dev/dri/card0)
By filtering out duplicate drm devices we avoid these confusing messages.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>