drm: bridge: icn6211: Add I2C configuration support

The ICN6211 chip starts in I2C configuration mode after cold boot.
Implement support for configuring the chip via I2C in addition to
the current DSI LP command mode configuration support. The later
seems to be available only on chips which have additional MCU on
the panel/bridge board which preconfigures the ICN6211, while the
I2C configuration mode added by this patch does not require any
such MCU.

Acked-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
To: dri-devel@lists.freedesktop.org
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220331150509.9838-10-marex@denx.de