Revert and fix "drm/i915/dp: remove DPMS mode tracking from DP"
Revert and fix "drm/i915/dp: remove DPMS mode tracking from DP"

This reverts commit 885a50147f00a8a80108904bf58a18af357717f3.

We actually *do* need to track DPMS state so that on hotplug, we don't
retrain the link until DPMS is disabled.

However, that code had avery small bug -- it wouldn't set the
dpms_mode at mode set time, and so link retraining would not actually
occur on monitor hotplug until the monitor had gone through a DPMS
off/DPMS on cycle.

Signed-off-by: Keith Packard <fd7f967895e9f35e58ec8a62a847a54d7fa7275f@keithp.com>
Tested-by: Andrew Lutomirski <2cc0d0d76de2e6f37b92deeb83c85cb306fc5dc1@mit.edu>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs