drm/i915: restore QUIRK_NO_PCH_PWM_ENABLE

drm/i915: restore QUIRK_NO_PCH_PWM_ENABLE

This reverts the bisected regressing

commit bc0bb9fd1c7810407ab810d204bbaecb255fddde
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Thu Nov 14 12:14:29 2013 +0200

    drm/i915: remove QUIRK_NO_PCH_PWM_ENABLE

restoring QUIRK_NO_PCH_PWM_ENABLE for a couple of Dell XPS models which
broke in 3.14.

There is no such revert upstream. We have root caused and fixed the
issue upstream, without the quirk, with:

commit 39fbc9c8f6765959b55e0b127dd5c57df5a47d67
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Apr 9 11:22:06 2014 +0300

    drm/i915: check VBT for supported backlight type

and

commit c675949ec58ca50d5a3ae3c757892f1560f6e896
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Apr 9 11:31:37 2014 +0300

    drm/i915: do not setup backlight if not available according to VBT

While the commits are within the stable rules otherwise, and fix more
machines than just the regressed Dell XPS models, we feel backporting
them to stable may be too risky. The revert is limited to the broken
machines, and the impact should be effectively the same as what the
upstream commits do more generally.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76276
Reported-by: Romain Francoise <romain@orebokech.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Tested-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Romain Francoise <romain@orebokech.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>