drm: fix return value in auth function

This just fixes up the return value in the drm_auth:remove_magic

Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/drm_auth.c b/drivers/char/drm/drm_auth.c
index 40cd262..c7b19d3 100644
--- a/drivers/char/drm/drm_auth.c
+++ b/drivers/char/drm/drm_auth.c
@@ -121,7 +121,7 @@
 
 	drm_free(pt, sizeof(*pt), DRM_MEM_MAGIC);
 
-	return -EINVAL;
+	return 0;
 }
 
 /**