s390x/cpumodel: generate CPU feature group lists

s390x/cpumodel: generate CPU feature group lists

Feature groups will be very helpful to reduce the amount of features
typically available in sane configurations. E.g. the MSA facilities
introduced loads of subfunctions, which could - in theory - go away
in the future, but we want to avoid reporting hundrets of features to
the user if usually all of them are in place.

Groups only contain features that were introduced in one shot, not just
random features. Therefore, groups can never change. This is an important
property regarding migration.

Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Message-Id: <20160905085244.99980-7-dahi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>