[PATCH] mv643xx_eth: Cache align skb->data if CONFIG_NOT_COHERENT_CACHE

When I/O is non-cache-coherent, we need to ensure that the I/O buffers
we use don't share cache lines with other data.

Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>