Merge branch 'mptcp-fixes'

Matthieu Baerts says:

====================
mptcp: fixes for v6.2

Patch 1 clears resources earlier if there is no more reasons to keep
MPTCP sockets alive.

Patches 2 and 3 fix some locking issues visible in some rare corner
cases: the linked issues should be quite hard to reproduce.

Patch 4 makes sure subflows are correctly cleaned after the end of a
connection.

Patch 5 and 6 improve the selftests stability when running in a slow
environment by transfering data for a longer period on one hand and by
stopping the tests when all expected events have been observed on the
other hand.

All these patches fix issues introduced before v6.2.
====================

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