drm: bridge: Add waveshare DSI2DPI unit driver

Waveshare touchscreen consists of a DPI panel and a driver board.
The waveshare driver board consists of ICN6211 and a MCU to
convert DSI to DPI and control the backlight.
This driver treats the MCU and ICN6211 board as a whole unit.
It can support all resolution waveshare DSI2DPI based panel,
the timing table should come from 'panel-dpi' panel in the device tree.

Signed-off-by: Joseph Guo <qijian.guo@nxp.com>
Suggested-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250806-waveshare-v3-3-fd28e01f064f@nxp.com