T7673: Add patch linux-cp fix multicast route updates on address add/del

[sever-sever]

Change Summary

Required for keepalive multicast mode. Patch from upstream

linux-cp: fix multicast route updates on address add/del
Ensure multicast routes are only added when the first IPv4 address is configured on an interface,
and only removed when the last address is deleted.

This prevents premature removal or redundant addition of multicast routes during address changes.

Type: fix

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Other (please describe): Add/update patches

Related Task(s)

• https://vyos.dev/T7673

Related PR(s)

Proposed changes

How to test

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

[sever-sever]

Build checked, looks fine

vyos_bld@4e59669a0f1c:/vyos/work/tmp/build-vpp/vyos-build/scripts/package-build/vpp$ ls -la | grep deb
-rw-r--r--  1 vyos_bld vyos_bld    230540 Jul 31 16:27 libvppinfra_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld    160408 Jul 31 16:27 libvppinfra-dev_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld     28560 Jul 31 16:27 python3-vpp-api_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld   5303592 Jul 31 16:27 vpp_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld 151313232 Jul 31 16:27 vpp-dbg_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld   1420780 Jul 31 16:27 vpp-dev_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld   6251776 Jul 31 16:27 vpp-plugin-core_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld    382880 Jul 31 16:27 vpp-plugin-devtools_24.10.0-22~g96e8a93df_amd64.deb
-rw-r--r--  1 vyos_bld vyos_bld   4985504 Jul 31 16:27 vpp-plugin-dpdk_24.10.0-22~g96e8a93df_amd64.deb
vyos_bld@4e59669a0f1c:/vyos/work/tmp/build-vpp/vyos-build/scripts/package-build/vpp$