staging: octeon: support fixed-link phys

Support fixed-link PHYs. This allows to remove some of the board-specific
link cvmx_helper code in the future.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>