drm: Stop resetting connector state to unknown

It's causing piles of issues since we've stopped forcing full detect
cycles in the sysfs interfaces with

commit c484f02d
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Mar 6 12:36:42 2015 +0000

    drm: Lighten sysfs connector 'status'

The original justification for this was that the hpd handlers could
use the unknown state as a hint to force a full detection. But current
i915 code isn't doing that any more, and no one else really uses reset
on resume. So instead just keep the old state around.

References: http://article.gmane.org/gmane.comp.freedesktop.xorg.drivers.intel/62584
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=100641


Cc: Rui Matos <tiagomatos@gmail.com>
Cc: Julien Wajsberg <felash@gmail.com>
Cc: kuddel.mail@gmx.de
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: stable@vger.kernel.org
Acked-by: Rob Clark <robdclark@gmail.com>
Tested-by: Rui Tiago Cação Matos <tiagomatos@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>