staging: dpaa2-switch: setup buffer pool and RX path rings

Allocate and setup a buffer pool, needed on the Rx path of the control
interface. Also, define the Rx buffer size seen by the WRIOP from the
PAGE_SIZE buffers seeded.

Also, create the needed Rx rings for both frame queues used on the
control interface.  On the Rx path, when a pull-dequeue operation is
performed on a software portal, available frame descriptors are put in a
ring - a DMA memory storage - for further usage.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>