drm/i915/skl: Remove the check enforcing VCS2 to be gen8 only

We already track this in the intel_info struct.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
[danvet: Make the commit message a bit less terse.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>