hw/9pfs : open brace '{' following struct go on the same line

Fix code style. Open braces for struct should go on the same line.

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: <20201030043515.1030223-2-zhangxinhao1@huawei.com>
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>