Merge branch 'selftests-Add-ethtool-and-scale-tests'

Ido Schimmel says:

====================
selftests: Add ethtool and scale tests

This patch set adds generic ethtool tests and a mlxsw-specific router
scale test for Spectrum-2.

Patches #1-#2 from Danielle add the router scale test for Spectrum-2. It
re-uses the same test as Spectrum-1, but it is invoked with a different
scale, according to what it is queried from devlink-resource.

Patches #3-#5 from Amit are a re-work of the ethtool tests that were
posted in the past [1]. Patches #3-#4 add the necessary library
routines, whereas patch #5 adds the test itself. The test checks both
good and bad flows with autoneg on and off. The test plan it detailed in
the commit message.

Last time Andrew and Florian (copied) provided very useful feedback that
is incorporated in this set. Namely:

* Parse the value of the different link modes from
  /usr/include/linux/ethtool.h
* Differentiate between supported and advertised speeds and use the
  latter in autoneg tests
* Make the test generic and move it to net/forwarding/ instead of being
  mlxsw-specific

[1] https://patchwork.ozlabs.org/cover/1112903/
====================

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