drm/msm/dp: Drop now unused hpd_high member

Since '8ede2ecc ("drm/msm/dp: Add DP compliance tests on Snapdragon
Chipsets")' the hpd_high member of struct dp_usbpd has been write-only.

Let's clean up the code a little bit by removing the writes as well.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20211106172246.2597431-1-bjorn.andersson@linaro.org


Signed-off-by: Rob Clark <robdclark@chromium.org>