hw/xwin: Fix command line arguments for multiple monitors.

Moving Xwin to a certain monitor using "-screen 0 @2" would fail,
printing "ddxProcessArgument - screen - Querying monitors failed".

This happened since commit 3ead1d810b,
because EnumDisplayMonitor() returns FALSE if its callback function
returns FALSE (which is not clearly documented), and QueryMonitor()
would then also return FALSE.

Moving back to the old behaviour, where the return value of
EnumDisplayMonitors() is ignored.

Reviewed-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>

hw/xwin/winmonitors.c

@@ -64,5 +64,7 @@ QueryMonitor(int index, struct GetMonitorInfoData *data)
     data->requestedMonitor = index;
 
     /* query information */
-    return EnumDisplayMonitors(NULL, NULL, getMonitorInfo, (LPARAM) data);
+    EnumDisplayMonitors(NULL, NULL, getMonitorInfo, (LPARAM) data);
+
+    return TRUE;
 }