drm/i915: Make sure all planes and connectors are added on modeset.

Add missing calls to drm_atomic_add_affected_*. This is needed
to convert to atomic planes. When converting to atomic all planes
are needed on modeset. For good measure make sure all connectors
are added too.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>