drm/panel: Update TODO list item for cleaning up prepared/enabled tracking

Now that most panels have been updated not to track/double-check their
prepared/enabled state update the TODO with next steps.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240604172305.v3.23.I104cdece7324b0c365e552a17f9883414ffaea01@changeid


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240604172305.v3.23.I104cdece7324b0c365e552a17f9883414ffaea01@changeid