drm/tve200: Replace custom connector with panel bridge

This replaces the custom connector in the TVE200 with the
panel bridge helper. As long as we're just using panels
and no other bridges, this works just fine.

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20170902200711.29298-1-linus.walleij@linaro.org