drm/i915: Nuke the LVDS lid notifier

We broke the LVDS notifier resume thing in (presumably) commit
e2c8b870 ("drm/i915: Use atomic helpers for suspend, v2.") as
we no longer duplicate the current state in the LVDS notifier and
thus we never resume it properly either.

Instead of trying to fix it again let's just kill off the lid
notifier entirely. None of the machines tested thus far have
apparently needed it. Originally the lid notifier was added to
work around cases where the VBIOS was clobbering some of the
hardware state behind the driver's back, mostly on Thinkpads.
We now have a few report of Thinkpads working just fine without
the notifier. So maybe it was misdiagnosed originally, or
something else has changed (ACPI video stuff perhaps?).

If we do end up finding a machine where the VBIOS is still causing
problems I would suggest that we first try setting various bits in
the VBIOS scratch registers. There are several to choose from that
may instruct the VBIOS to steer clear.

With the notifier gone we'll also stop looking at the panel status
in ->detect().

v2: Nuke enum modeset_restore (Rodrigo)

Cc: stable@vger.kernel.org
Cc: Wolfgang Draxinger <wdraxinger.maillist@draxit.de>
Cc: Vito Caputo <vcaputo@pengaru.com>
Cc: kitsunyan <kitsunyan@airmail.cc>
Cc: Joonas Saarinen <jza@saunalahti.fi>
Tested-by: Vito Caputo <vcaputo@pengaru.com> # Thinkapd X61s
Tested-by: kitsunyan <kitsunyan@airmail.cc> # ThinkPad X200
Tested-by: Joonas Saarinen <jza@saunalahti.fi> # Fujitsu Siemens U9210
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105902
References: https://lists.freedesktop.org/archives/intel-gfx/2018-June/169315.html
References: https://bugs.freedesktop.org/show_bug.cgi?id=21230
Fixes: e2c8b870

 ("drm/i915: Use atomic helpers for suspend, v2.")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180717174216.22252-1-ville.syrjala@linux.intel.com
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>