Merge branch 'mlxsw-refactor-qdisc-offload'

Petr Machata says:

====================
mlxsw: Refactor qdisc offload

Currently, mlxsw admits for offload a suitable root qdisc, and its
children. Thus up to two levels of hierarchy are offloaded. Often, this is
enough: one can configure TCs with RED and TCs with a shaper, and can even
see counters for each TC by looking at a qdisc at a sufficiently shallow
position.

While simple, the system has obvious shortcomings. It is not possible to
configure both RED and shaping on one TC. It is not possible to place a
PRIO below root TBF, which would then be offloaded as port shaper. FIFOs
are only offloaded at root or directly below, which is confusing to users,
because RED and TBF of course have their own FIFO.

This patchset is a step towards the end goal of allowing more comprehensive
qdisc tree offload and cleans up the qdisc offload code.

- Patches #1-#4 contain small cleanups.

- Up until now, since mlxsw offloaded only a very simple qdisc
  configurations, basically all bookkeeping was done using one container
  for the root qdisc, and 8 containers for its children. Patches #5, #6, #8
  and #9 gradually introduce a more dynamic structure, where parent-child
  relationships are tracked directly at qdiscs, instead of being implicit.

- This tree management assumes only one qdisc is created at a time. In FIFO
  handlers, this condition was enforced simply by asserting RTNL lock. But
  instead of furthering this RTNL dependence, patch #7 converts the whole
  qdisc offload logic to a per-port mutex.

- Patch #10 adds a selftest.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>