NIU: Add Sun CP3260 ATCA blade support

This patch adds support for the Sun CP3260 ATCA blade which is
a N2 based ATCA blade with 2 NIU ports. The NIU ports do not
have on-board PHY.

Signed-off-by: Santwona Behera <santwona.behera@sun.com>
Signed-off-by: David S. Miller <davem@davemloft.net>