After 7f1bdec5 our nodedev driver is capable of
determining DRM devices (DRM stands for Direct Render Manager not
Digital rights management). There is still one bit missing
though: virConnectListAllNodeDevices() is capable of listing
either all devices or just those with specified capability. Well,
DRM capability is missing there.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>