hw/pc_piix: remove is_default for pc-0.15

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/pc_piix.c b/hw/pc_piix.c
index 17f8d5d..2fc4211 100644
--- a/hw/pc_piix.c
+++ b/hw/pc_piix.c
@@ -385,7 +385,6 @@
     .desc = "Standard PC",
     .init = pc_init_pci,
     .max_cpus = 255,
-    .is_default = 1,
 };
 
 static QEMUMachine pc_machine_v0_14 = {