mv643xx_eth: mbus decode window support

Make it possible to pass mbus_dram_target_info to the mv643xx_eth
driver via the platform data, and make the mv643xx_eth driver
program the window registers based on this data if it is passed in.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Reviewed-by: Tzachi Perelstein <tzachi@marvell.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Dale Farnsworth <dale@farnsworth.org>