staging: lustre: libcfs: declare internal symbols as static

Fixes sparse warnings like:
  warning: symbol '...' was not declared. Should it be static?

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Cc: Peng Tao <bergwolf@gmail.com>
Cc: Jinshan Xiong <jinshan.xiong@intel.com>
Cc: Srikrishan Malik <srikrishanmalik@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>