Staging: octeon-ethernet: Assign proper MAC addresses.

Allocate MAC addresses using the same method as the bootloader.  This
avoids changing the MAC between bootloader and kernel operation as
well as avoiding duplicates and use of addresses outside of the
assigned range.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>