Merge branch 'mptcp-allow-privileged-operations-from-user-ns-cleanup'

Matthieu Baerts says:

====================
mptcp: allow privileged operations from user ns & cleanup

This series allows privileged Netlink operations from user namespaces. When a
non-root user configures MPTCP endpoints, the memory allocation is now accounted
to this user. See patches 4 and 5.

Apart from that, there are some cleanup:

 - Patch 1 adds a macro to improve code readability

 - Patch 2 regroups similar checks all together

 - Patch 3 uses an explicit boolean instead of a counter to do one more check
====================

Link: https://lore.kernel.org/r/20220906205545.1623193-1-matthieu.baerts@tessares.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>