gprs_ns2: fix wrong format string in Tx Size logline

Don't use %u for integer.

Change-Id: I324836ec4943c97f0dbc16ade697c468eba02b35
diff --git a/src/gb/gprs_ns2_message.c b/src/gb/gprs_ns2_message.c
index ad115ef..03e26bd 100644
--- a/src/gb/gprs_ns2_message.c
+++ b/src/gb/gprs_ns2_message.c
@@ -798,7 +798,7 @@
 		msgb_tv16_put(msg, NS_IE_IPv6_EP_NR, ip6_ep_nr);
 
 	LOG_NS_SIGNAL(nsvc, "Tx", nsh->pdu_type, LOGL_INFO,
-		      " (reset=%u, max_nr_nsvc=%u, num_ip4=%u, num_ip6=%u)\n",
+		      " (reset=%u, max_nr_nsvc=%u, num_ip4=%d, num_ip6=%d)\n",
 		      reset_flag, max_nr_nsvc, ip4_ep_nr, ip6_ep_nr);
 	return ns_vc_tx(nsvc, msg);
 }