s390x/cpumodel: introduce CPU features

s390x/cpumodel: introduce CPU features

The patch introduces s390x CPU features (most of them refered to as
facilities) along with their discription and some functions that will be
helpful when working with the features later on.

Please note that we don't introduce all known CPU features, only the
ones currently supported by KVM + QEMU. We don't want to enable later
on blindly any facilities, for which we don't know yet if we need QEMU
support to properly support them (e.g. migrate additional state when
active). We can update QEMU later on.

Acked-by: Cornelia Huck <[email protected]>
Signed-off-by: Michael Mueller <[email protected]>
Signed-off-by: David Hildenbrand <[email protected]>
[reworked to include non-stfle features, added definitions]
Message-Id: <20160905085244[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>