egl: Don't add hardware device if there is no render node v2.

Do not offer a hardware drm backed egl device if no render node
is available. The current implementation will fail on this
egl device. On top it issues a warning that is actually missleading.
There are finally more error paths that can fail on the way to a
hardware backed egl device. Fixing all of them would kind of require
opening the drm device and see if there is a usable driver associated
with the device. The taken approach avoids a full probe and fixes at
least this kind of problem on kvm virtualization hosts I observe here.

Fixes: dbb4457d ("egl: add EGL_EXT_device_drm support")
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>