netfilter: remove duplicated include

Remove duplicated include.
Signed-off-by: Nicolas Kaiser <nikai@nikai.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/netfilter/xt_ipvs.c

@@ -16,7 +16,6 @@
 #include <linux/ip_vs.h>
 #include <linux/types.h>
 #include <linux/netfilter/x_tables.h>
-#include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_ipvs.h>
 #include <net/netfilter/nf_conntrack.h>