iptables-xml: resolve compiler warnings

iptables-xml.c: In function "parse_counters":
iptables-xml.c:70:8: warning: assignment from incompatible pointer type
iptables-xml.c:71:8: warning: assignment from incompatible pointer type

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/iptables-xml.c b/iptables-xml.c
index daf4208..32d996a 100644
--- a/iptables-xml.c
+++ b/iptables-xml.c
@@ -64,7 +64,7 @@
 static int
 parse_counters(char *string, struct ipt_counters *ctr)
 {
-	u_int64_t *pcnt, *bcnt;
+	__u64 *pcnt, *bcnt;
 
 	if (string != NULL) {
 		pcnt = &ctr->pcnt;