Revert "ethtool: Add n-tuple string length to drvinfo and return it"

This reverts commit c79c5ffdce14abb4de3878c5aa8c3c6e5093c69b.

As Jeff points out we can't break the user visible interface
like this, we need to add this into the reserved[] thing.

Signed-off-by: David S. Miller <davem@davemloft.net>