Merge branch 'dsa-qca8k-fixes'

Christian Marangi says:

====================
net: dsa: qca8k: multiple fix on mdio read/write

Due to some problems in reading the Documentation and elaborating it
some wrong assumption were done. The error was reported and notice only
now due to how things are setup in the code flow.

First 2 patch fix mgmt eth where the lenght calculation is very
confusing and in step of word size. (the related commit description have
an extensive description about how this mess works)

Last 3 patch revert the broken mdio cache and apply a correct version
that should still save some extra mdio in phy poll secnario.

These 5 patch fix each related problem and apply what the Documentation
actually say.

Changes v2:
- Add cover letter
- Fix typo in revert patch
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Signed-off-by: David S. Miller <davem@davemloft.net>