Merge branch 'macb-ethtool-ringparam'

Zach Brown says:

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macb: Add ethtool get_ringparam and set_ringparam to cadence

There are use cases like RT that would benefit from being able to tune the
macb rx/tx ring sizes. The ethtool set_ringparam function is the standard way
of doing so.

The first patch changes the hardcoded tx/rx ring sizes to variables that are
set to a hardcoded default.

The second patch implements the get_ringparam and set_ringparam fucntions.
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Signed-off-by: David S. Miller <davem@davemloft.net>