drm: Carry over the stereo flags when adding the alternate mode

This allows to expose the alternate clock versions of the stereo modes.

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/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 48f1746..c24af1d 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2507,6 +2507,9 @@
 		if (!newmode)
 			continue;
 
+		/* Carry over the stereo flags */
+		newmode->flags |= mode->flags & DRM_MODE_FLAG_3D_MASK;
+
 		/*
 		 * The current mode could be either variant. Make
 		 * sure to pick the "other" clock for the new mode.