net: socionext: get rid of huge dma sync in netsec_alloc_rx_data

Socionext driver can run on dma coherent and non-coherent devices.
Get rid of huge dma_sync_single_for_device in netsec_alloc_rx_data since
now the driver can let page_pool API to managed needed DMA sync

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>