drm/msm/dp: Drop now unused hpd_high member

drm/msm/dp: Drop now unused hpd_high member

[ Upstream commit fabae667b1263216be53e0230cd3966a9a1963a4 ]

Since '8ede2ecc3e5e ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>