intel/devinfo: fix missing num_thread_per_eu on ICL

There was an assumption that num_thread_per_eu would be set in the
Gen8 features. Since this is mostly the same of all gen8->11 (except
GEN9_LP that overwrites it) let's just factor it out.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: mesa-stable@lists.freedesktop.org
Acked-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
(cherry picked from commit 773e6aa9)