The "ps2" bus is only available on certain machines like x86. On
machines like s390x, we should refuse to add a device to this bus
instead of silently ignoring it.

Looking at the QEMU sources, PS/2 is only available if the QEMU binary
has the "i8042" device, so let's check for that and only allow "ps2"
devices if this QEMU device is available, or if we're on x86 anyway
(so we don't have to fake the QEMU_CAPS_DEVICE_I8042 capability in
all the tests that use <input ... bus='ps2'/> in their xml data).
Reported-by: NSebastian Mitterle <smitterl@redhat.com>
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1763191Signed-off-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>