For use in the next patch, take the current is-coherent helper and add
it to i915_gem_object.h
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170222114049.28456-2-chris@chris-wilson.co.uk