drm/i915: Remove connectors_active from sanitization, v2.

connectors_active will be removed, so just calculate this instead.

Changes since v1:
- Look for the right pointer in intel_sanitize_encoder.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>