MIPS jazz: create isa bus

As i8259 in mips_jazz.c is not correctly connected to the isa bus, the
mc146818rtc isa devices fails to be created.
Signed-off-by: NRoy Tam <roytam@gmail.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

hw/mips_jazz.c

@@ -185,6 +185,8 @@ void mips_jazz_init (ram_addr_t ram_size,
 
     /* ISA devices */
     i8259 = i8259_init(env->irq[4]);
+    isa_bus_new(NULL);
+    isa_bus_irqs(i8259);
     DMA_init(0);
     pit = pit_init(0x40, i8259[0]);
     pcspk_init(pit);