net: mvpp2: sync RX data at the hardware packet offset

net: mvpp2: sync RX data at the hardware packet offset

mvpp2 programs the RX queue packet offset, so hardware writes received
data at dma_addr + MVPP2_SKB_HEADROOM. The current CPU sync starts at
dma_addr and only covers rx_bytes + MVPP2_MH_SIZE bytes, which syncs the
unused headroom and misses the same number of bytes at the packet tail.

On non-coherent DMA systems this can leave the CPU reading stale cache
contents for the end of the received frame.

Use dma_sync_single_range_for_cpu() with MVPP2_SKB_HEADROOM as the range
offset so the sync covers the Marvell header and packet data actually
written by hardware.

Fixes: e1921168bbd4 ("mvpp2: sync only the received frame")
Signed-off-by: Til Kaiser <mail@tk154.de>
Link: https://patch.msgid.link/20260607134943.21996-2-mail@tk154.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>