Merge branch 'net-Extend-availability-of-PHY-statistics'

Florian Fainelli says:

====================
net: Extend availability of PHY statistics

This patch series adds support for retrieving PHY statistics with DSA switches
when the CPU port uses a PHY to PHY connection (as opposed to MAC to MAC).
To get there a number of things are done:

- first we move the code dealing with PHY statistics outside of net/core/ethtool.c
  and create helper functions since the same code will be reused
- then we allow network device drivers to provide an ethtool_get_phy_stats callback
  when the standard PHY library helpers are not suitable
- we update the DSA functions dealing with ethtool operations to get passed a
  stringset instead of assuming ETH_SS_STATS like they currently do
- then we provide a set of standard helpers within DSA as a framework and add
  the plumbing to allow retrieving the PHY statistics of the CPU port(s)
- finally plug support for retrieving such PHY statistics with the b53 driver

Changes in v3:

- retrict the b53 change to 539x and 531x5 series of switches
- added a change to dsa_loop.c to help test the feature

Changes in v2:

- got actual testing when the DSA master network device has a PHY that
  already provides statistics (thanks Nikita!)

- fixed the kbuild error reported when CONFIG_PHYLIB=n

- removed the checking of ops which is redundant and not needed
====================

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