drm: remove the EDID blob stored in the EDID property when it is disconnected

Now the EDID property will be updated when the corresponding EDID can be
obtained from the external display device. But after the external device
is plugged-out, the EDID property is not updated. In such case we still
get the corresponding EDID property although it is already detected as
disconnected.

https://bugs.freedesktop.org/show_bug.cgi?id=26743Signed-off-by: NZhao Yakui <yakui.zhao@intel.com>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_crtc_helper.c

@@ -104,6 +104,7 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 	if (connector->status == connector_status_disconnected) {
 		DRM_DEBUG_KMS("%s is disconnected\n",
 			  drm_get_connector_name(connector));
+		drm_mode_connector_update_edid_property(connector, NULL);
 		goto prune;
 	}