drm/bridge: it66121: Add minimal it66122 support

drm/bridge: it66121: Add minimal it66122 support

The IT66122 is a pin compatible replacement for the IT66122. Based on
empirical testing, the new device looks to be compatible with IT66121.
However due to a lack of public data sheet at this time beyond overall
feature list[1] (which seems to add additional features vs ITT66121),
it is hard to determine that additional register operations required
to enable additional features.

So, introduce the device as a new compatible that we will detect based
on vid/pid match, with explicit id that can be used to extend the
driver capability as information becomes available later on.

[1] https://www.ite.com.tw/en/product/cate1/IT66122

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Andrew Davis <afd@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20251029150636.3118628-6-nm@ti.com