drm/i915: Kill GTT mappings when moving from GTT domain

In order to force a page-fault on a GTT mapping after we start using it
from the GPU and so enforce correct CPU/GPU synchronisation, we need to
invalidate the mapping.

Pointed out by Owain G. Ainsworth.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
1 file changed