drm/i915/lspcon: Remove DPCD compare based resume time workaround

This effectively reverts
commit 489375c8
Author: Imre Deak <imre.deak@intel.com>
Date:   Mon Oct 24 19:33:31 2016 +0300

    drm/i915/lspcon: Add workaround for resuming in PCON mode

The workaround was added without considering that HPD is low during
the failed AUX transfers the WA fixed. Since the previous patch we
wait for HPD to get asserted. My tests also show that this happens
_after_ the DPCD reads start to return correct values. This
suggests that we don't need this WA any more, let's try to remove
it to reduce the clutter.

Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1485509961-9010-4-git-send-email-imre.deak@intel.com