iotests: Revert "iotests: use -ccw on s390x for 040, 139, and 182"

Commit f1d5516a introduces a test in some iotests to check if
the machine is a s390-ccw-virtio and to select virtio-*-ccw rather
than virtio-*-pci.

We don't need that because QEMU already provides aliases to use the correct
virtio interface according to the machine type.

This patch removes all virtio-*-pci and virtio-*-ccw to use virtio-*
instead and remove get_virtio_scsi_device().
This also enables virtio-mmio devices (virtio-*-device)

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20210319202335.2397060-5-laurent@vivier.eu>
Message-Id: <20210323165308.15244-20-alex.bennee@linaro.org>