pc-bios/s390-ccw/virtio: Set missing status bits while initializing

According chapter "3.1.1 Driver Requirements: Device Initialization"
of the Virtio specification (v1.1), a driver for a device has to set
the ACKNOWLEDGE and DRIVER bits in the status field after resetting
the device. The s390-ccw bios skipped these steps so far and seems
like QEMU never cared. Anyway, it's better to follow the spec, so
let's set these bits now in the right spots, too.

Message-Id: <20220704111903.62400-7-thuth@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>