drm: Make exposing stereo modes a per-connector opt-in

Just like with interlaced or double scan modes, make stereo modes a
per-connector opt-in to give a chance to driver authors to make it work
before enabling it.

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 6b7f9c7..1b69407 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -108,6 +108,7 @@
     MODE_ONE_HEIGHT,    /* only one height is supported */
     MODE_ONE_SIZE,      /* only one resolution is supported */
     MODE_NO_REDUCED,    /* monitor doesn't accept reduced blanking */
+    MODE_NO_STEREO,	/* stereo modes not supported */
     MODE_UNVERIFIED = -3, /* mode needs to reverified */
     MODE_BAD = -2,	/* unspecified reason */
     MODE_ERROR	= -1	/* error condition */
@@ -611,6 +612,7 @@
 	int connector_type_id;
 	bool interlace_allowed;
 	bool doublescan_allowed;
+	bool stereo_allowed;
 	struct list_head modes; /* list of modes on this connector */
 
 	enum drm_connector_status status;