Fix stream timing clear for all GUIDs for a port

AbstractPort uses a value of UINT_MAX to signify 'all guids', but
StreamTiming uses 'invalid guid' value which are NOT the same value. But
UINT_MAX is guaranteed to be greater than invalid GUID - so instead of
equality we check for greater than comparison.

server/streamtiming.cpp

@@ -100,7 +100,7 @@ void StreamTiming::clear(uint portId, uint guid)
     if (!portTiming)
         return;
 
-    if (guid == SignProtocol::kInvalidGuid)
+    if (guid >= SignProtocol::kInvalidGuid)
         portTiming->clear();      // remove ALL guids
     else
         portTiming->remove(guid);