Merge branch 'net-stmmac-Improvements-and-Selftests'

Jose Abreu says:

====================
net: stmmac: Improvements and Selftests

[ Thanks to the introducion of selftests this series ended up being a misc
of improvements and the selftests additions per-se. ]

This introduces selftests support in stmmac driver. We add 9 basic sanity
checks and MAC loopback support for all cores within the driver. This way
more tests can easily be added in the future and can be run in virtually
any MAC/GMAC/QoS/XGMAC platform.

Having this we can find regressions and missing features in the driver
while at the same time we can check if the IP is correctly working.

We have been using this for some time now and I do have more tests to
submit in the feature. My experience is that although writing the tests
adds more development time, the gain results are obvious.

I let this feature optional within the driver under a Kconfig option.
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Signed-off-by: David S. Miller <davem@davemloft.net>