Merge branch 'net-phy-broadcom-cable-tester-support'

Michael Walle says:

====================
net: phy: broadcom: cable tester support

Add cable tester support for the Broadcom PHYs. Support for it was
developed on a BCM54140 Quad PHY which RDB register access.

If there is a link partner the results are not as good as with an open
cable. I guess we could retry if the measurement until all pairs had at
least one valid result.

changes since v1:
 - added Reviewed-by: tags
 - removed "div by 2" for cross shorts, just mention it in the commit
   message. The results are inconclusive if the tests are repeated. So
   just report the length as is for now.
 - fixed typo in commit message
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Signed-off-by: David S. Miller <davem@davemloft.net>