Merge branch 'netlink-specs-rt-link-decode-ip6gre'

Jakub Kicinski says:

====================
netlink: specs: rt-link: decode ip6gre

Adding GRE tunnels to the .config for driver tests caused
some unhappiness in YNL, as it can't decode all the link
attrs on the system. Add ip6gre support to fix the tests.
This is similar to commit 6ffdbb93 ("netlink: specs:
rt_link: decode ip6tnl, vti and vti6 link attrs").
====================

Link: https://patch.msgid.link/20250603135357.502626-1-kuba@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>