mv643xx_eth: Split off mv643xx_eth platform device data

The mv643xx ethernet silicon block is also found in a couple of other
Marvell chips.  As a first step towards splitting off the mv643xx_eth
bits from the rest of the mv643xx bits, this patch splits the mv643xx
ethernet platform device data struct in linux/mv643xx.h off into
linux/mv643xx_eth.h, and includes the latter from the former.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Acked-by: Tzachi Perelstein <tzachi@marvell.com>
Signed-off-by: Dale Farnsworth <dale@farnsworth.org>