selinux: ensure av_permissions.h is built when needed

The Makefile rule responsible for building flask.h and
av_permissions.h only lists flask.h as a target which means that
av_permissions.h is only generated when flask.h needs to be
generated.  This patch fixes this by adding av_permissions.h as a
target to the rule.

Fixes: 8753f6bec3 ("selinux: generate flask headers during kernel build")
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/Makefile

@@ -26,5 +26,5 @@ quiet_cmd_flask = GEN     $(obj)/flask.h $(obj)/av_permissions.h
       cmd_flask = $< $(obj)/flask.h $(obj)/av_permissions.h
 
 targets += flask.h av_permissions.h
-$(obj)/flask.h: scripts/selinux/genheaders/genheaders FORCE
+$(obj)/flask.h $(obj)/av_permissions.h &: scripts/selinux/genheaders/genheaders FORCE
 	$(call if_changed,flask)