drm/i915/icl: Add command cache invalidate

On the set of invalidations, we need to add command
cache invalidate as a new domain.

Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190815083055.14132-2-mika.kuoppala@linux.intel.com