Let's add support for being able to read the HPD pin even if it's
hooked directly to the controller. This will let us take away the
waiting in the AUX transfer functions of the eDP controller drivers.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220614145327.v4.3.I9ee239f6b95b944c8fa030f300ad222a7af9899d@changeid