net: Add Marvell Kirkwood gigabit ethernet driver

This patch adds a egiga driver for the Marvell Kirkwood SoC's.

Contributors:
Yotam Admon <yotam@marvell.com>
Michael Blostein <michaelbl@marvell.com

Reviewed-by: Ronen Shitrit <rshitrit@marvell.com>
Acked-by: Stefan Rose <sr@denx.de>
Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>