media: tegra-video: Add support for external sensor capture

This patch adds support to capture from the external sensor
based on device graph in the device tree.

Driver walks through the device graph to create media links
between the entities and registers and unregisters video devices
when the corresponding sub-devices are bound and unbound.

Channel formats are enumerated based on available formats from
the sensor and the corresponding matched formats from the Tegra
supported video formats list.

Each Tegra CSI instance can be configured as 4-lane or 2-lane
based on supported lane configuration from the sensor through
the device tree.

Currently this driver supports V4L2 video node centric only.

[hverkuil: changed video_unregister_device to vb2_video_unregister_device]

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>