drm/i915: Share the common force-audio property between connectors

Make the audio property creation routine common and share the single
property between the connectors.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 71bd6f5..f63ee16 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -716,6 +716,7 @@
 	struct intel_fbdev *fbdev;
 
 	struct drm_property *broadcast_rgb_property;
+	struct drm_property *force_audio_property;
 
 	atomic_t forcewake_count;
 } drm_i915_private_t;