commit 6dc5df71 upstream.

Fix undefined reference issue reported by kbuild test robot.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>