mv643xx_eth: allow multiple RX queues

Allow the platform code to specify that we are running on hardware
that is capable of supporting multiple RX queues.  If this option
is used, initialise all of the given RX queues instead of just RX
queue zero.

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