microblaze: fix leak of fdevice tree blob

The device tree blob returned by load_device_tree is malloced.
Free it before returning.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

hw/microblaze/boot.c

@@ -100,6 +100,7 @@ static int microblaze_load_dtb(hwaddr addr,
     }
 
     cpu_physical_memory_write(addr, fdt, fdt_size);
+    g_free(fdt);
     return fdt_size;
 }