Merge branch 'ipv6-snmp-avoid-performance-issue-with-ratelimithost'

Eric Dumazet says:

====================
ipv6: snmp: avoid performance issue with RATELIMITHOST

Addition of ICMP6_MIB_RATELIMITHOST in commit d0941130c9351
("icmp: Add counters for rate limits") introduced a performance drop
in case of DOS (like receiving UDP packets to closed ports).

Per netns ICMP6_MIB_RATELIMITHOST tracking uses per-cpu storage and
is enough, we do not need per-device and slow tracking for this metric.

In v2 of this series, I completed the removal of SNMP_MIB_SENTINEL
in all the kernel for consistency.

v1: https://lore.kernel.org/20250904092432.113c4940@kernel.org
====================

Link: https://patch.msgid.link/20250905165813.1470708-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>