drm/panel-edp: add fat warning against adding new panel compatibles

drm/panel-edp: add fat warning against adding new panel compatibles

Add a fat warning against adding new panel compatibles to the panel-edp
driver. All new users of the eDP panels are supposed to use the generic
"edp-panel" compatible device on the AUX bus. The remaining compatibles
are either used by the existing DT or were used previously and are
retained for backwards compatibility.

Suggested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240614-edp-panel-drop-v4-1-4e0a112eec46@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>