media: tegra-video: Add support for V4L2_EVENT_SOURCE_CHANGE

Current implementation uses v4l2_ctrl_subscribe_event() and this
does not handle V4L2_EVENT_SOURCE_CHANGE.

So, update driver to handle V4L2_EVENT_SOURCE_CHANGE.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>