audit: correct audit_filter_inodes() definition

After changes in commit 0590b933 ("fixing audit rule ordering mess,
part 1"), audit_filter_inodes() returns void, so if CONFIG_AUDITSYSCALL
not defined, it should be do {} while(0).

Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>