drm/i915/kbl: Add KBL GT2 sku

Adding a missing GT2 sku discovered off hardware.

Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
Reviewed-by: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1524522483-19987-1-git-send-email-matthew.s.atwood@intel.com