S390: Re-enable capability probing for virtio devices.

Since we switched to QMP probing, the object types are spelled out
explicitly, i.e. virtio-net-pci. This has effectively disabled
the capability detection of s390 virtio devices. The trivial fix
is to add the s390 virtio types explicitly to qemuCapsObjectProps.
Signed-off-by: NViktor Mihajlovski <mihajlov@linux.vnet.ibm.com>

src/qemu/qemu_capabilities.c

@@ -1400,6 +1400,10 @@ static struct qemuCapsObjectTypeProps qemuCapsObjectProps[] = {
       ARRAY_CARDINALITY(qemuCapsObjectPropsVirtioBlk) },
     { "virtio-net-pci", qemuCapsObjectPropsVirtioNet,
       ARRAY_CARDINALITY(qemuCapsObjectPropsVirtioNet) },
+    { "virtio-blk-s390", qemuCapsObjectPropsVirtioBlk,
+      ARRAY_CARDINALITY(qemuCapsObjectPropsVirtioBlk) },
+    { "virtio-net-s390", qemuCapsObjectPropsVirtioNet,
+      ARRAY_CARDINALITY(qemuCapsObjectPropsVirtioNet) },
     { "pci-assign", qemuCapsObjectPropsPciAssign,
       ARRAY_CARDINALITY(qemuCapsObjectPropsPciAssign) },
     { "kvm-pci-assign", qemuCapsObjectPropsPciAssign,