qemu: set 'devno' property to order additional NICs on s390x

On s390x, network interfaces use the CCW bus instead of PCI, which can lead to
wrong NIC ordering. This causes the team-dhcp-via-ignition test to fail:
```
07:19:05  Jul 29 07:19:00 qemu0 kola-runext-test.sh[2336]: Error: get team0 ip = 10.0.2.32, expected is 10.0.2.31
```

This happens, because eth1 and eth2 are wrong ordered (altnames):
```
$ ip -o link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000\    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000\    link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff\    altname enc2\    altname enx525400123456
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master team0 state UP mode DEFAULT group default qlen 1000\    link/ether 52:55:00:d1:56:01 brd ff:ff:ff:ff:ff:ff\    altname enc4\    altname enx525500d15601
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master team0 state UP mode DEFAULT group default qlen 1000\    link/ether 52:55:00:d1:56:01 brd ff:ff:ff:ff:ff:ff permaddr 52:55:00:d1:56:00\    altname enc3\    altname enx525500d15600
5: team0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000\    link/ether 52:55:00:d1:56:01 brd ff:ff:ff:ff:ff:ff
```

Issue: coreos/fedora-coreos-tracker#1992

Signed-off-by: Nikita Dubrovskii <[email protected]>

Author: nikita-dubrovskii

mantle/platform/qemu.go

@@ -705,6 +705,13 @@ func (builder *QemuBuilder) setupAdditionalNetworking() error {
 
 		netdev := fmt.Sprintf("user,id=eth%s,dhcpstart=10.0.2.%s", idSuffix, netSuffix)
 		device := virtio(builder.architecture, "net", fmt.Sprintf("netdev=eth%s,mac=52:55:00:d1:56:%s", idSuffix, macSuffix))
+		// On s390x, devices use the CCW bus instead of PCI, which may cause them to appear in a different order.
+		// By default, the CSSID is 0xFE and the SSID is 0x0. For additional NICs, set the SSID to 0x1
+		// to avoid interference with other CCW devices
+		if builder.architecture == "s390x" {
+			device += fmt.Sprintf(",devno=fe.1.%04x", i)
+		}
+
 		builder.Append("-netdev", netdev, "-device", device)
 		macCounter++
 	}