Merge branch 'net-prepare-for-removal-of-net-dev_index_head'

Eric Dumazet says:

====================
net: prepare for removal of net->dev_index_head

This series changes rtnl_fdb_dump, last iterator using net->dev_index_head[]

First patch creates ndo_fdb_dump_context structure, to no longer
assume specific layout for the arguments.

Second patch adopts for_each_netdev_dump() in rtnl_fdb_dump(),
while changing two first fields of ndo_fdb_dump_context.

Third patch removes the padding, thus changing the location
of ctx->fdb_idx now that all users agree on how to retrive it.

After this series, the only users of net->dev_index_head
are __dev_get_by_index() and dev_get_by_index_rcu().

We have to evaluate if switching them to dev_by_index xarray
would be sensible.

v1: https://lore.kernel.org/20241207162248.18536-1-edumazet@google.com/T/#m800755d4b16c7f335927a76d9f52ebd37f7f077c
====================

Link: https://patch.msgid.link/20241209100747.2269613-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>