vga_switcheroo: simplify the return expression of vga_switcheroo_runtime_resume

Simplify the return expression.

Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200921131110.93365-1-miaoqinglang@huawei.com