Merge branch 'mv88e6xxx-Disable-ports-to-save-power'

Andrew Lunn says:

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mv88e6xxx: Disable ports to save power

Save some power by disabling ports. The first patch fully disables a
port when it is runtime disabled. The second disables any ports which
are not used at all.

Depending on configuration strapping, this can lower the temperature
of an idle switch a few degrees.
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Signed-off-by: David S. Miller <davem@davemloft.net>