Merge branch 'dsa-mv88e6xxx-cleanup-Global-Control-2-register'

Vivien Didelot says:

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net: dsa: mv88e6xxx: cleanup Global Control 2 register

The mv88e6xxx driver still writes arbitrary values in the Global 1
Control 2 register at setup, which layout differs a lot between chips.
This results in an inconsistent configuration, for example with the
Remote Management Unit (RMU).

The first patch adds an operation for the Cascade Port bits, the second
patch sets the device number in the device mapping function and the
third patch adds an operation to correctly disable the RMU.
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Signed-off-by: David S. Miller <davem@davemloft.net>