Fix code style. Operator needs spaces both sides.

Signed-off-by: Xinhao Zhang <zhangxinhao1@huawei.com>
Signed-off-by: Kai Deng <dengkai1@huawei.com>
Reported-by: Euler Robot <euler.robot@huawei.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <20201030043515.1030223-1-zhangxinhao1@huawei.com>
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>