drm/i915: Only commit active planes when updating planes during reset.

In the next commit commit_plane will no longer check if the crtc is active.
To prevent issues with legacy page flips the check should be performed inside
update_primary_planes.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>