drm/i915/kbl: Add REVID macro

Add REVID macro for kbl to limit wa applicability to particular
revision range.

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-4-git-send-email-mika.kuoppala@intel.com