Merge branch 'net-bpf-nd_tbl-fixes-for-when-ipv6-disable-1'

Ricardo B. Marlière says:

====================
{net,bpf}: nd_tbl fixes for when ipv6.disable=1

Please consider merging these four patches to fix three crashes that were
found after this report:

https://lore.kernel.org/all/CAHXs0ORzd62QOG-Fttqa2Cx_A_VFp=utE2H2VTX5nqfgs7LDxQ@mail.gmail.com

The first patch from Jakub Kicinski is a preparation in order to enable
the use ipv6_mod_enabled() even when CONFIG_IPV6=n.
====================

Link: https://patch.msgid.link/20260307-net-nd_tbl_fixes-v4-0-e2677e85628c@suse.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>