drm/nouveau: Fix crashes during fbcon init on single head cards.

this fixes a regression since the fbcon rework.
Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/nouveau_fbcon.c

@@ -387,7 +387,8 @@ int nouveau_fbcon_init(struct drm_device *dev)
 	dev_priv->nfbdev = nfbdev;
 	nfbdev->helper.funcs = &nouveau_fbcon_helper_funcs;
 
-	ret = drm_fb_helper_init(dev, &nfbdev->helper, 2, 4);
+	ret = drm_fb_helper_init(dev, &nfbdev->helper,
+				 nv_two_heads(dev) ? 2 : 1, 4);
 	if (ret) {
 		kfree(nfbdev);
 		return ret;