drm/bridge: ps8640: Add software to support aux defer

This chip can not handle aux defer if the host directly program
its aux registers to access edid/dpcd. So we need let software
to handle the aux defer situation.

Signed-off-by: Jason Yen <jason.yen@paradetech.corp-partner.google.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220930042506.2529522-1-jason.yen@paradetech.corp-partner.google.com