selinux: cleanup exit_sel_fs() declaration

exit_sel_fs() has been removed since commit f22f9aaf ("selinux:
remove the runtime disable functionality").
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/include/security.h

@@ -384,7 +384,6 @@ struct selinux_kernel_status {
 extern void selinux_status_update_setenforce(int enforcing);
 extern void selinux_status_update_policyload(int seqno);
 extern void selinux_complete_init(void);
-extern void exit_sel_fs(void);
 extern struct path selinux_null;
 extern void selnl_notify_setenforce(int val);
 extern void selnl_notify_policyload(u32 seqno);