Merge branch 'mptcp-fixes-and-cleanup-for-v6-7'

Mat Martineau says:

====================
mptcp: Fixes and cleanup for v6.7

This series includes three initial patches that we had queued in our
mptcp-net branch, but given the likely timing of net/net-next syncs this
week, the need to avoid introducing branch conflicts, and another batch
of net-next patches pending in the mptcp tree, the most practical route
is to send everything for net-next.

Patches 1 & 2 fix some intermittent selftest failures by adjusting timing.

Patch 3 removes an unneccessary userspace path manager restriction on
the removal of subflows with subflow ID 0.

The remainder of the patches are all cleanup or selftest changes:

Patches 4-8 clean up kernel code by removing unused parameters, making
more consistent use of existing helper functions, and reducing extra
casting of socket pointers.

Patch 9 removes an unused variable in a selftest script.

Patch 10 adds a little more detail to some mptcp_join test output.
====================

Link: https://lore.kernel.org/r/20231025-send-net-next-20231025-v1-0-db8f25f798eb@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>