drm: try harder to avoid regression when merging mode bits

For QXL hw we really want the bits to be replaced as we change
the preferred mode on the fly, and the same goes for virgl when
I get to it, however the original fix for this seems to have caused
a wierd regression on Intel G33 that in a stunning display of failure
at opposition to his normal self, Daniel failed to diagnose.

So we are left doing this, ugly ugly ugly ugly, Daniel you fixed
that G33 yet?, ugly, ugly.

Tested-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 36a5feb..f51c839 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -165,6 +165,10 @@
 extern int drm_helper_probe_single_connector_modes(struct drm_connector
 						   *connector, uint32_t maxX,
 						   uint32_t maxY);
+extern int drm_helper_probe_single_connector_modes_nomerge(struct drm_connector
+							   *connector,
+							   uint32_t maxX,
+							   uint32_t maxY);
 extern void drm_kms_helper_poll_init(struct drm_device *dev);
 extern void drm_kms_helper_poll_fini(struct drm_device *dev);
 extern bool drm_helper_hpd_irq_event(struct drm_device *dev);