s390x: modularize virtio-gpu-ccw

s390x: modularize virtio-gpu-ccw

Since the virtio-gpu-ccw device depends on the hw-display-virtio-gpu
module, which provides the type virtio-gpu-device, packaging the
hw-display-virtio-gpu module as a separate package that may or may not
be installed along with the qemu package leads to problems. Namely if
the hw-display-virtio-gpu is absent, qemu continues to advertise
virtio-gpu-ccw, but it aborts not only when one attempts using
virtio-gpu-ccw, but also when libvirtd's capability probing tries
to instantiate the type to introspect it.

Let us thus introduce a module named hw-s390x-virtio-gpu-ccw that
is going to provide the virtio-gpu-ccw device. The hw-s390x prefix
was chosen because it is not a portable device.

With virtio-gpu-ccw built as a module, the correct way to package a
modularized qemu is to require that hw-display-virtio-gpu must be
installed whenever the module hw-s390x-virtio-gpu-ccw.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Tested-by: Halil Pasic <pasic@linux.ibm.com>
Message-Id: <20210317095622.2839895-4-kraxel@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>