media: staging: tegra-vde: Mark tegra_vde_runtime_suspend/resume as __maybe_unused

If CONFIG_PM is not set, gcc warns:

drivers/staging/media/tegra-vde/vde.c:916:12:
 warning: 'tegra_vde_runtime_suspend' defined but not used [-Wunused-function]

Make it __maybe_unused to fix this.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>