drm/i915: Make ggtt invalidation work on ggtt

It is more logical for ggtt invalidation to take ggtt as input parameter.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190621070811.7006-20-tvrtko.ursulin@linux.intel.com