drm/fb-helper: Propagate errors from initial config failure

Make drm_fb_helper_initial_config() return an int rather than a bool so
that the error can be properly propagated. While at it, update drivers
to propagate errors further rather than just ignore them.

v2:
- cirrus: No cleanup is required, the top-level cirrus_driver_load()
  will do it as part of cirrus_driver_unload() in its cleanup path.
  Reported-by: Fengguang Wu <fengguang.wu@intel.com>

Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
[danvet: Squash in simplification patch from kbuild.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/mgag200/mgag200_fb.c

@@ -303,14 +303,22 @@ int mgag200_fbdev_init(struct mga_device *mdev)
 	if (ret)
 		return ret;
 
-	drm_fb_helper_single_add_all_connectors(&mfbdev->helper);
+	ret = drm_fb_helper_single_add_all_connectors(&mfbdev->helper);
+	if (ret)
+		goto fini;
 
 	/* disable all the possible outputs/crtcs before entering KMS mode */
 	drm_helper_disable_unused_functions(mdev->dev);
 
-	drm_fb_helper_initial_config(&mfbdev->helper, bpp_sel);
+	ret = drm_fb_helper_initial_config(&mfbdev->helper, bpp_sel);
+	if (ret)
+		goto fini;
 
 	return 0;
+
+fini:
+	drm_fb_helper_fini(&mfbdev->helper);
+	return ret;
 }
 
 void mgag200_fbdev_fini(struct mga_device *mdev)