MIPS: Octeon: Fix management port MII address on Kontron S1901

Management port MII address is incorrect on Kontron S1901 resulting
in broken networking. Fix by providing definitions for the in-tree DT
pruning code.

Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Acked-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10914/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>