rust: pl011: fix repr(C) for PL011Class

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/hw/char/pl011/src/device.rs

@@ -123,6 +123,7 @@ pub struct PL011State {
 
 qom_isa!(PL011State : SysBusDevice, DeviceState, Object);
 
+#[repr(C)]
 pub struct PL011Class {
     parent_class: <SysBusDevice as ObjectType>::Class,
     /// The byte string that identifies the device.