net: mvneta: get rid of huge dma sync in mvneta_rx_refill

Get rid of costly dma_sync_single_for_device in mvneta_rx_refill
since now the driver can let page_pool API to manage needed DMA
sync with a proper size.

- XDP_DROP DMA sync managed by mvneta driver:	~420Kpps
- XDP_DROP DMA sync managed by page_pool API:	~585Kpps

Tested-by: Matteo Croce <mcroce@redhat.com>
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>