drm/nouveau: fix suspend/resume when in headless mode

Backport of fixes from upstream commit:
9430738

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/nouveau/nouveau_drv.c

@@ -188,11 +188,13 @@ nouveau_pci_suspend(struct pci_dev *pdev, pm_message_t pm_state)
 	if (dev->switch_power_state == DRM_SWITCH_POWER_OFF)
 		return 0;
 
-	NV_INFO(dev, "Disabling display...\n");
-	nouveau_display_fini(dev);
+	if (dev->mode_config.num_crtc) {
+		NV_INFO(dev, "Disabling display...\n");
+		nouveau_display_fini(dev);
 
-	NV_INFO(dev, "Disabling fbcon...\n");
-	nouveau_fbcon_set_suspend(dev, 1);
+		NV_INFO(dev, "Disabling fbcon...\n");
+		nouveau_fbcon_set_suspend(dev, 1);
+	}
 
 	NV_INFO(dev, "Unpinning framebuffer(s)...\n");
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
@@ -359,10 +361,12 @@ nouveau_pci_resume(struct pci_dev *pdev)
 			NV_ERROR(dev, "Could not pin/map cursor.\n");
 	}
 
-	nouveau_fbcon_set_suspend(dev, 0);
-	nouveau_fbcon_zfill_all(dev);
+	if (dev->mode_config.num_crtc) {
+		nouveau_fbcon_set_suspend(dev, 0);
+		nouveau_fbcon_zfill_all(dev);
 
-	nouveau_display_init(dev);
+		nouveau_display_init(dev);
+	}
 
 	/* Force CLUT to get re-loaded during modeset */
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {