Fix build: forgot to qualify tcpip.TCPStats.

Change-Id: Icd66ada27a391a3165b2768a82ac93b004091df1
diff --git a/tcpip/stack/stack.go b/tcpip/stack/stack.go
index 8fd6e6d..cffa94c 100644
--- a/tcpip/stack/stack.go
+++ b/tcpip/stack/stack.go
@@ -151,7 +151,7 @@
 		UnknownNetworkEndpointRcvdPackets: atomic.LoadUint64(&s.stats.UnknownNetworkEndpointRcvdPackets),
 		MalformedRcvdPackets:              atomic.LoadUint64(&s.stats.MalformedRcvdPackets),
 		DroppedPackets:                    atomic.LoadUint64(&s.stats.DroppedPackets),
-		TCP: TCPStats{
+		TCP: tcpip.TCPStats{
 			ActiveConnectionOpenings:  atomic.LoadUint64(&s.stats.TCP.ActiveConnectionOpenings),
 			PassiveConnectionOpenings: atomic.LoadUint64(&s.stats.TCP.PassiveConnectionOpenings),
 			FailedConnectionAttempts:  atomic.LoadUint64(&s.stats.TCP.FailedConnectionAttempts),