drm/nouveau/fbcon: fix module unload when fbcon init has failed for some reason

BugLink: https://bugs.launchpad.net/bugs/1892822

[ Upstream commit 498595ab ]

Stale pointer was tripping up the unload path.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/gpu/drm/nouveau/nouveau_fbcon.c

@@ -566,6 +566,7 @@ nouveau_fbcon_init(struct drm_device *dev)
 	drm_fb_helper_fini(&fbcon->helper);
 free:
 	kfree(fbcon);
+	drm->fbcon = NULL;
 	return ret;
 }