drm/panel-edp: Add powered_on_to_enable delay

Add the support of powered_on_to_enable delay as the minimum time that
needs to have passed between the panel powered on and enable may begin.

This delay is seen in BOE panels as the minimum delay of T3+T4+T5+T6+T8
in the eDP timing diagrams.

Signed-off-by: Pin-yen Lin <treapking@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231214152817.2766280-2-treapking@chromium.org