tools: silence compilation warnings

  CC       gtp-link.o
gtp-link.c: In function ‘main’:
gtp-link.c:48:40: warning: unused variable ‘flags’ [-Wunused-variable]
  unsigned int seq, portid, change = 0, flags = 0;
                                        ^
gtp-link.c:48:28: warning: unused variable ‘change’ [-Wunused-variable]
  unsigned int seq, portid, change = 0, flags = 0;
                            ^
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/tools/gtp-link.c b/tools/gtp-link.c
index 8aa9e98..b82bd37 100644
--- a/tools/gtp-link.c
+++ b/tools/gtp-link.c
@@ -45,7 +45,7 @@
 	struct nlmsghdr *nlh;
 	struct ifinfomsg *ifm;
 	int ret;
-	unsigned int seq, portid, change = 0, flags = 0;
+	unsigned int seq, portid;
 	struct nlattr *nest, *nest2;
 
 	if (argc != 3) {