mv643xx_eth: move port_receive() into its only caller

The port_receive() function is a remnant of the original mv643xx_eth
HAL split.  This patch moves port_receive() into its caller, so that
the top and the bottom half of RX processing no longer communicate
via the HAL FUNC_RET_STATUS/pkt_info mechanism abstraction anymore.

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