migration: fix off-by-one in buffered_rate_limit

Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NReviewed-by: Eric Blake <eblake@redhat.com>

migration.c

@@ -632,7 +632,7 @@ static int buffered_rate_limit(void *opaque)
         return ret;
     }
 
-    if (s->bytes_xfer > s->xfer_limit) {
+    if (s->bytes_xfer >= s->xfer_limit) {
         return 1;
     }