staging/lustre: Make nrs_policy_get_info_locked() static

This patch fixes the warning generated by sparse: "symbol 'nrs_policy_get_info_locked' was not
declared. Should it be static?" by declaring the function static.

Signed-off-by: Rocco Folino <rocco@devzen.net>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>