Merge branch 'ipv4-namespacify-ipv4-address-hash-table'

Kuniyuki Iwashima says:

====================
ipv4: Namespacify IPv4 address hash table.

This is a prep of per-net RTNL conversion for RTM_(NEW|DEL|SET)ADDR.

Currently, each IPv4 address is linked to the global hash table, and
this needs to be protected by another global lock or namespacified to
support per-net RTNL.

Adding a global lock will cause deadlock in the rtnetlink path and GC,

  rtnetlink                      check_lifetime
  |- rtnl_net_lock(net)          |- acquire the global lock
  |- acquire the global lock     |- check ifa's netns
  `- put ifa into hash table     `- rtnl_net_lock(net)

so we need to namespacify the hash table.

The IPv6 one is already namespacified, let's follow that.

v2: https://lore.kernel.org/netdev/20241004195958.64396-1-kuniyu@amazon.com/
v1: https://lore.kernel.org/netdev/20241001024837.96425-1-kuniyu@amazon.com/
====================

Link: https://patch.msgid.link/20241008172906.1326-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>