Merge branch 'mptcp-unify-pm-interfaces'

Matthieu Baerts says:

====================
mptcp: unify PM interfaces

These patches from Geliang better isolate the two MPTCP path-managers by
avoiding calling userspace PM functions from the in-kernel PM. Instead,
new functions declared in pm.c directly dispatch to the right PM.

In addition to have a clearer code, this also avoids a bit of duplicated
checks.

This is a refactoring, there is no behaviour change intended here.
====================

Link: https://lore.kernel.org/r/20230608-upstream-net-next-20230608-mptcp-unify-pm-interfaces-v1-0-b301717c9ff5@tessares.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>