test: fix a ninja test failure for vaapioverlay.
test: fix a ninja test failure for vaapioverlay.

That test case only works with drm display, so the build such as

meson -Dwith_x11=yes -Dwith_wayland=no -Dwith_drm=no -Dwith_egl=no
-Dwith_glx=no

gets a failure when run ninja test. Just enable this test when drm
is enabled.

ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi