core: reqorked check for incompatible modes of bind_ipv6_link_local

(cherry picked from commit f7045d1c08d37e91ee7e96e415c06b218aee98fd)

src/core/cfg.y

@@ -987,7 +987,8 @@ assign_stm:
 	| IPV6_HEX_STYLE error { yyerror("string value expected"); }
 	| BIND_IPV6_LINK_LOCAL EQUAL NUMBER {
 		sr_bind_ipv6_link_local = $3;
-		if(!(sr_bind_ipv6_link_local && (KSR_IPV6_LINK_LOCAL_BIND|KSR_IPV6_LINK_LOCAL_SKIP))) {
+		if((sr_bind_ipv6_link_local & KSR_IPV6_LINK_LOCAL_BIND)
+				&& (sr_bind_ipv6_link_local & KSR_IPV6_LINK_LOCAL_SKIP)) {
 			yyerror("incompatible modes set");
 		}
 	}