dt-bindings: media: renesas,isp: Add Gen4 family fallback

dt-bindings: media: renesas,isp: Add Gen4 family fallback

The ISP Channel Selector IP is the same for all current Gen4 devices.
This was not known when adding support for V3U and V4H and a single SoC
specific compatible was used.

Before adding more SoC specific bindings for V4M add a family compatible
fallback for Gen4. That way the driver only needs to be updated once for
Gen4, and we still have the option to fix any problems in the driver if
any testable differences between the SoCs are found.

There are already DTS files using the V3U and V4H compatibles which
needs to be updated to not produce a warning for DTS checks. The driver
also needs to kept the compatible values to be backward compatible , but
for new Gen4 SoCs such as V4M we can avoid this.

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