staging/lustre: remove unused function

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Cc: Peng Tao <bergwolf@gmail.com>
Cc: HPDD-discuss@lists.01.org
Cc: devel@driverdev.osuosl.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>