selinux: sparse fix: eliminate warnings for selinuxfs

Fixes several sparse warnings for selinuxfs.c

Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index 30002c4..13b6263 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -218,6 +218,9 @@
 extern void selinux_status_update_policyload(int seqno);
 extern void selinux_complete_init(void);
 extern int selinux_disable(void);
+extern void exit_sel_fs(void);
+extern struct dentry *selinux_null;
+extern struct vfsmount *selinuxfs_mount;
 
 #endif /* _SELINUX_SECURITY_H_ */