[NIU]: Support for Marvell PHY

From: Mirko Lindner <mlindner@marvell.com>

This patch makes necessary changes in the Neptune driver to support
the new Marvell PHY. It also adds support for the LED blinking
on Neptune cards with Marvell PHY. All registers are using defines
in the niu.h header file as is already done for the BCM8704 registers.

[ Coding style, etc. cleanups -DaveM ]

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