Revert "drm/i915/fbc: Allow on unfenced surfaces, for recent gen"

Revert "drm/i915/fbc: Allow on unfenced surfaces, for recent gen"

This reverts commit 3bbb95aa1204 ("drm/i915/fbc: Allow on unfenced surfaces,
for recent gen") as Skylake has issues with unfenced FBC tracking (and
yes Skylake doesn't even enable FBC yet). Paulo would like to do a full
review of all existing workarounds to see if any more are missing prior
to allowing FBC on unfenced surfaces. In the meantime lets hope that all
framebuffers are idle and naturally fit within the mappable aperture.

Requested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Fixes: 3bbb95aa1204 ("drm/i915/fbc: Allow on unfenced surfaces...");
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160824180053.24239-1-chris@chris-wilson.co.uk
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>