Description of problem:
update interface with passt backend by update-device report successfully, but no changes for passt related parameters

Version-Release number of selected component (if applicable):
libvirt-9.0.0-4.el9.x86_64
passt-0^20221110.g4129764-1.el9.x86_64
qemu-kvm-7.2.0-8.el9.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Start a vm with interface as below:
$ virsh dumpxml test --xpath //interface
<interface type="user">
<mac address="52:54:00:bc:fa:5e"/>
<source dev="eno1"/>
<ip address="172.17.2.4" family="ipv4" prefix="24"/>
<ip address="2001:db8:ac10:fd01::20" family="ipv6"/>
<model type="virtio"/>
<backend type="passt" logFile="/home/test/passt.log"/>
<alias name="net0"/>
<address type="pci" domain="0x0000" bus="0x08" slot="0x00" function="0x0"/>
</interface>

2. Try to update the interface by update-device to add the port forwarding setting:
$ cat interface.xml
<interface type="user">
<mac address="52:54:00:bc:fa:5e"/>
<source dev="eno1"/>
<ip address="172.17.2.4" family="ipv4" prefix="24"/>
<ip address="2001:db8:ac10:fd01::20" family="ipv6"/>
<model type="virtio"/>
<portForward proto="tcp">
<range start="31339" to="41339"/>
</portForward>
<backend type="passt" logFile="/home/test/passt.log"/>
<alias name="net0"/>
<address type="pci" domain="0x0000" bus="0x08" slot="0x00" function="0x0"/>
</interface>

$ virsh update-device test interface.xml
Device updated successfully

3. check the live xml, there is no changes
$ virsh dumpxml test --xpath //interface
<interface type="user">
<mac address="52:54:00:bc:fa:5e"/>
<source dev="eno1"/>
<ip address="172.17.2.4" family="ipv4" prefix="24"/>
<ip address="2001:db8:ac10:fd01::20" family="ipv6"/>
<model type="virtio"/>
<backend type="passt" logFile="/home/test/passt.log"/>
<alias name="net0"/>
<address type="pci" domain="0x0000" bus="0x08" slot="0x00" function="0x0"/>
</interface>

Actual results:
update-device report succeed, but there is no changes

Expected results:
The passt related parameters may not support update on the fly, so the live update should fail.

Additional info:
live update to update the link state for passt backend interface succeed and network work properly