[CLEANUP] config: use warnif_cond_requires_resp() to check for bad ACLs

Factor out some repetitive copy-pasted code to check for request ACLs
validity.
diff --git a/include/proto/acl.h b/include/proto/acl.h
index b65a2b3..ec9963d 100644
--- a/include/proto/acl.h
+++ b/include/proto/acl.h
@@ -98,7 +98,7 @@
 /* Reports a pointer to the first ACL used in condition <cond> which requires
  * at least one of the USE_FLAGS in <require>. Returns NULL if none matches.
  */
-struct acl *cond_find_require(struct acl_cond *cond, unsigned int require);
+struct acl *cond_find_require(const struct acl_cond *cond, unsigned int require);
 
 /* Return a pointer to the ACL <name> within the list starting at <head>, or
  * NULL if not found.