mv643xx_eth: kill FUNC_RET_STATUS/pkt_info

Since they are no longer used, kill enum FUNC_RET_STATUS and
struct pkt_info (which were a rather roundabout way of communicating
RX/TX status within the same driver).

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