drm/i915: Move Braswell stop_machine GGTT insertion workaround

drm/i915: Move Braswell stop_machine GGTT insertion workaround

There was a silent conflict between

commit 4bb7569f5b62e9ada44ab06837178b0f5e71c0f9
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Oct 15 14:23:01 2015 +0200

    drm/i915: restore ggtt double-bind avoidance

and

commit 119d064f9e206c1fddc1c8a1ae7d7600ec563470
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Oct 23 18:43:32 2015 +0100

    drm/i915: Serialise updates to GGTT with access through GGTT on Braswell

thankfully caught by the extra WARN safegaurd in 4bb7569f. Since we now
override the GGTT insert_pages callback when installing the aliasing
ppgtt, we assert that the callback is the original ggtt routine.
However, on Braswell we now use a different insertion routine to
serialise access through the GGTT with updating the PTE and hence the
conflict. To avoid the conflict, move the custom insertion routine for
Braswell down a level.

Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1447859979-20107-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: drm-intel-fixes@lists.freedesktop.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit c140330b5e6b5bc2262ffb2f50bfeea06a482699)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>