media: rcar-csi2: Add support for R-Car V4M

media: rcar-csi2: Add support for R-Car V4M

The V4M is the second Gen4 device that is enabled in the rcar-csi2
driver. There is much overlap with the already supported V4H device. The
registers that where new on Gen4 and where added with the V4H prefix are
retained and only new registers unique to the V4M are added with the new
V4M prefix. This follows the style for when V4H was added which had an
overlap with Gen3 registers.

The V4M CSI-2 receiver supports D-PHY mode only, either in 1-, 2- or
4-lane configuration. The datasheets do not document lane swapping and
is left out for now.

While the V4M only supports D-PHY the configuration for it is added in
such a way that it can be reused for V4H which supports both C-PHY and
D-PHY. No known SoC exists to test the D-PHY configuration on V4H so
it's not wired-up.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>