Use DeviceClass rather than SysBusDeviceClass in
tusb6010_class_init().

Cc: kraxel@redhat.com
Signed-off-by: NMao Zhongyi <maozhongyi@cmss.chinamobile.com>
Signed-off-by: NZhang Shengju <zhangshengju@cmss.chinamobile.com>
Message-id: 20181130093852.20739-20-maozhongyi@cmss.chinamobile.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>