drm/i915/skl: Split the SKL PCI ids by GT

We need to have a separate GT3 struct intel_device_info to declare they
have a second VCS. Let's start by splitting the PCI ids per-GT.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>