s390x/css: introduce css data stream

This is a preparation for introducing handling for indirect data
addressing and modified indirect data addressing (CCW). Here we introduce
an interface which should make the addressing scheme transparent for the
client code. Here we implement only the basic scheme (no IDA or MIDA).

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Message-Id: <20170921180841.24490-2-pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
2 files changed