net: mvneta: move header prefetch in mvneta_swbm_rx_frame

Move data buffer prefetch in mvneta_swbm_rx_frame after
dma_sync_single_range_for_cpu

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