Fix free use in xen_backend.c

xen_backend.c is using qemu_free() instead of free().
Fix it.

Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/xen_backend.c

@@ -594,7 +594,7 @@ static void xenstore_update(void *unused)
 	xenstore_update_fe(vec[XS_WATCH_PATH], (void*)ptr);
 
 cleanup:
-    qemu_free(vec);
+    free(vec);
 }
 
 static void xen_be_evtchn_event(void *opaque)