Merge branch 'vxlan-vnifilter-fix-vni-add-update-notifications'

Andy Roulin says:

====================
vxlan: vnifilter: fix VNI add/update notifications

When a vxlan device has vnifilter enabled, userspace observers
(e.g., bridge monitor vni) miss VNI add events and see spurious
notifications on no-op VNI re-adds.

Patch 1 fixes the missing notification on VNI add: vxlan_vni_add()
guarded the notification on a 'changed' flag that vxlan_vni_update_group()
only sets when a multicast group or remote is supplied, so VNIs added
without a group (e.g., L3 VXLAN) were silently created.

Patch 2 fixes the spurious notification on VNI update: vxlan_vni_update()
tested 'if (changed)' against a bool pointer instead of dereferencing it,
so every re-add produced a notification regardless of whether anything
actually changed.

Patch 3 adds a selftest covering both bugs along with a few related
cases (add with remote, remote update, delete-nonexistent).
====================

Link: https://patch.msgid.link/20260602185138.253265-1-aroulin@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>