virt: vbox: simplify the return expression of vbg_input_open()

Simplify the return expression.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Link: https://lore.kernel.org/r/20200921131113.93459-1-miaoqinglang@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>