ip6tnl: Use <netinet/in.h> for in6_addr and stuff

<linux/in6.h> is not compatible with some versions of <netinet/in.h>.

Cc: Susant Sahani <susant@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Thomas Haller <thaller@redhat.com>

lib/route/link/ip6tnl.c

@@ -30,7 +30,7 @@
 #include <netlink/route/rtnl.h>
 #include <netlink-private/route/link/api.h>
 #include <linux/if_tunnel.h>
-#include <linux/in6.h>
+#include <netinet/in.h>
 
 #define IP6_TNL_ATTR_LINK          (1 << 0)
 #define IP6_TNL_ATTR_LOCAL         (1 << 1)