compositor-drm: Do not return an error when no connectors are configured
compositor-drm: Do not return an error when no connectors are configured

Returning an error when there are no connectors results in
weston terminating after that. That's not expected when
trying to get weston to start with zero drm outputs.

Signed-off-by: Armin Krezović <31ec4b88003c779f400d1506dcff569d5faae2fb@gmail.com>
Reviewed-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>

sir-murray/weston,sir-murray/weston,krezovic/weston,krezovic/weston