uhci: renumber uhci_handle_td return codes

Step #2 (separate for better bisectability): renumber so the silly '-1'
goes away.  Pick a range which doesn't overlap the old values.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-uhci.c

@@ -78,10 +78,10 @@
 #define NB_PORTS 2
 
 enum {
-    TD_RESULT_STOP_FRAME = -1,
-    TD_RESULT_COMPLETE   = 0,
-    TD_RESULT_NEXT_QH    = 1,
-    TD_RESULT_ASYNC      = 2,
+    TD_RESULT_STOP_FRAME = 10,
+    TD_RESULT_COMPLETE,
+    TD_RESULT_NEXT_QH,
+    TD_RESULT_ASYNC,
 };
 
 typedef struct UHCIState UHCIState;