drm: bridge: icn6211: Add HS/VS/DE polarity handling

The driver currently hard-codes HS/VS polarity to active-low and DE to
active-high, which is not correct for a lot of supported DPI panels.
Add the missing mode flag handling for HS/VS/DE polarity.

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/20220331150509.9838-4-marex@denx.de