net: axienet: add missing memory barriers

net: axienet: add missing memory barriers

commit 95978df6fa328df619c15312e65ece469c2be2d2 upstream.

This driver was missing some required memory barriers:

Use dma_rmb to ensure we see all updates to the descriptor after we see
that an entry has been completed.

Use wmb and rmb to avoid stale descriptor status between the TX path and
TX complete IRQ path.

Fixes: 8a3b7a252dca9 ("drivers/net/ethernet/xilinx: added Xilinx AXI Ethernet driver")
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>