drm: copy mode type in drm_mode_connector_list_update()

In commit 38d5487d, Keith explained:
    This patch simply merges the two mode type bits together; that seems
    reasonable to me, but perhaps only a subset of the bits should be
    used? None of these can be user defined as they all come from
    looking at just the hardware.

However, merging the bits means that a flag becomes sticky. It is not
possible, for example to update the mode type to remove the
DRM_MODE_TYPE_PREFERRED bit.

After a brief discussion with Dave Airlie on irc, it was agreed to
propose that change, instead of introducing another function to remove a
bit from exisiting modes type.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_modes.c

@@ -1041,7 +1041,7 @@ void drm_mode_connector_list_update(struct drm_connector *connector)
 				/* if equal delete the probed mode */
 				mode->status = pmode->status;
 				/* Merge type bits together */
-				mode->type |= pmode->type;
+				mode->type = pmode->type;
 				list_del(&pmode->head);
 				drm_mode_destroy(connector->dev, pmode);
 				break;