use XFER_LIMIT_RATIO consistently

commit 5b4e1eb769eee892b44d3f6b2369b05196442f59

missed this use.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

Reviewed-by: Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/migration.c b/migration.c
index c69e864..d6ec3e8 100644
--- a/migration.c
+++ b/migration.c
@@ -650,7 +650,7 @@
         new_rate = SIZE_MAX;
     }
 
-    s->xfer_limit = new_rate / 10;
+    s->xfer_limit = new_rate / XFER_LIMIT_RATIO;
 
 out:
     return s->xfer_limit;