drm/panel-edp: Split the delay structure out

In the case where we can read an EDID for a panel the only part of the
panel description that can't be found directly from the EDID is the
description of the delays. Let's break the delay structure out so that
we can specify just the delays for panels that are detected by EDID.

This is simple code motion. No functional change is intended.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210914132020.v5.10.I24f3646dd09954958645cc05c538909f169bf362@changeid