Merge branch 'rtnetlink-convert-rtnl_newlink-to-per-netns-rtnl'

Kuniyuki Iwashima says:

====================
rtnetlink: Convert rtnl_newlink() to per-netns RTNL.

Patch 1 - 3 removes __rtnl_link_unregister and protect link_ops by
its dedicated mutex to move synchronize_srcu() out of RTNL scope.

Patch 4 introduces struct rtnl_nets and helper functions to acquire
multiple per-netns RTNL in rtnl_newlink().

Patch 5 - 8 are to prefetch the peer device's netns in rtnl_newlink().

Patch 9 converts rtnl_newlink() to per-netns RTNL.

Patch 10 pushes RTNL down to rtnl_dellink() and rtnl_setlink(), but
the conversion will not be completed unless we support cases with
peer/upper/lower devices.

I confirmed v3 survived ./rtnetlink.sh; rmmod netdevsim.ko; without
lockdep splat.

v3: https://lore.kernel.org/20241107022900.70287-1-kuniyu@amazon.com
v2: https://lore.kernel.org/20241106022432.13065-1-kuniyu@amazon.com
v1: https://lore.kernel.org/20241105020514.41963-1-kuniyu@amazon.com
====================

Link: https://patch.msgid.link/20241108004823.29419-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>