Revert "drm/i915: fix infinite recursion on unbind due to ilk vt-d w/a"

This reverts commit eb1711bb.

It blows up the i915 seqno tracking, resulting in the

	BUG_ON(seqno == 0);

in i915_wait_request() triggering, which will cause lock-ups.

See for example
  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/903010
  https://lkml.org/lkml/2011/12/14/395



Reported-requested-and-tested-by: Dirk Hohndel <dirk@hohndel.org>
Reported-by: Richard Eames <Richard.Eames@flinders.edu.au>
Reported-by: Rocko Requin <rockorequin@hotmail.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Keith Packard <keithp@keithp.com>
Cc: Eric Anholt <eric@anholt.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>