s390-bios: Decouple channel i/o logic from virtio

Create a separate library for channel i/o related code. This decouples
channel i/o operations from virtio and allows us to make use of them for
the real dasd boot path.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1554388475-18329-6-git-send-email-jjherne@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
8 files changed