QIpPacketHeader: correct the type of hopLimit member

In other places, it's referenced as int.

Change-Id: Ic66f33a34d45208686ad0e229644d3ef33c55a62
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/network/socket/qabstractsocketengine_p.h

@@ -78,7 +78,7 @@ public:
     QHostAddress destinationAddress;
 
     uint ifindex;
-    qint16 hopLimit;
+    int hopLimit;
     quint16 senderPort;
     quint16 destinationPort;
 };