s390/kvm_virtio/linux-headers: remove traces of old virtio transport

s390/kvm_virtio/linux-headers: remove traces of old virtio transport

We no longer support the old s390 transport, neither does the newest
Linux kernel. Remove it from the linux header script as well as the
s390x virtio code.  We still should handle the VIRTIO_NOTIFY hypercall,
to tolerate early printk on older guest kernels without an sclp console.
We continue to ignore these events.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20171115154223.109991-1-borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>