Merge branch 'netpoll-move-out-netconsole-specific-functions'

Breno Leitao says:

====================
netpoll: move out netconsole-specific functions

netpoll and netconsole were created together and their code has
been intermixed in net/core/netpoll.c for decades. The result is
that netpoll exposes two send-side interfaces:

 * a generic "give me an sk_buff" path used by every stacked-device
   driver (bonding, team, vlan, bridge, macvlan, dsa),

 * a second path that takes raw bytes and builds a UDP/IP/Ethernet
   packet -- exclusively for netconsole.

The packet builder, an skb pool allocator, and several
netconsole-specific helpers all live next to the generic plumbing even
though no other consumer ever touches them.

Worse, every netpoll user pays for that overlap: struct netpoll carries
an skb_pool and a refill work_struct that only netconsole's find_skb()
ever reads from, and net-core has to review unrelated changes (TTL, hop
limit, IP ID generation, source MAC selection, pool sizing) just because
they happen to be coded inside netpoll.

This is a waste of memory for something useless.

This series splits the netconsole-specific code out:

 * netpoll_send_udp() and its private helpers (push_ipv6, push_ipv4,
push_eth, push_udp, netpoll_udp_checksum, find_skb) move into
drivers/net/netconsole.c, leaving netpoll with a single skb-only
send interface that is the same for every user.

The moves are one function per patch for reviewability; helpers are
temporarily EXPORT_SYMBOL_GPL'd while netpoll_send_udp() is still in
netpoll calling them, then those exports are dropped together once
netpoll_send_udp() itself moves.

The only new permanent export is zap_completion_queue(), needed because
find_skb() still drains the per-CPU TX completion queue before
allocating.

struct netpoll is unchanged in this series; making the pool itself
netconsole-private (and reclaiming the skb_pool / refill_wq fields for
the rest of netpoll's users) is the natural follow-up, once this patchset
lands.
====================

Link: https://patch.msgid.link/20260512-netconsole_split-v2-0-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>