net: mvpp2: use only one rx queue per port per CPU

The number of receive queue per port is :
 - MVPP2_DEFAULT_RXQ if in single queue mode
 - MVPP2_DEFAULT_RXQ * num_possible_cpus if in multi queue mode

with MVPP2_DEFAULT_RXQ = 4.

However, we don't use the extra rx queues at the moment, we really only
need one per port per CPU, until some more advanced classification rules
are implemented.

Suggested-by: Stefan Chulski <stefanc@marvell.com>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>