net: mvpp2: fix DMA address calculation in mvpp2_txq_inc_put()

When TX descriptors are filled in, the buffer DMA address is split
between the tx_desc->buf_phys_addr field (high-order bits) and
tx_desc->packet_offset field (5 low-order bits).

However, when we re-calculate the DMA address from the TX descriptor in
mvpp2_txq_inc_put(), we do not take tx_desc->packet_offset into
account. This means that when the DMA address is not aligned on a 32
bytes boundary, we end up calling dma_unmap_single() with a DMA address
that was not the one returned by dma_map_single().

This inconsistency is detected by the kernel when DMA_API_DEBUG is
enabled. We fix this problem by properly calculating the DMA address in
mvpp2_txq_inc_put().

Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>