Merge branch 'mptcp-cleanups'

Matthieu Baerts says:

====================
mptcp: a couple of cleanups and improvements

Patch 1 removes an unneeded address copy in subflow_syn_recv_sock().

Patch 2 simplifies subflow_syn_recv_sock() to postpone some actions and
to avoid a bunch of conditionals.

Patch 3 stops reporting limits that are not taken into account when the
userspace PM is used.

Patch 4 adds a new test to validate that the 'subflows' field reported
by the kernel is correct. Such info can be retrieved via Netlink (e.g.
with ss) or getsockopt(SOL_MPTCP, MPTCP_INFO).

---
Changes in v2:
- Patch 3/4's commit message has been updated to use the correct SHA
- Rebased on latest net-next
- Link to v1: https://lore.kernel.org/r/20230324-upstream-net-next-20230324-misc-features-v1-0-5a29154592bd@tessares.net
====================

Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>