Merge branch 'axienet-fixes'

Andy Chiu says:

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net: axienet: fix DMA Tx error

We ran into multiple DMA TX errors while writing files over a network
block device running on top of a DMA-connected AXI Ethernet device on
64-bit RISC-V machines. The errors indicated that the DMA had fetched a
null descriptor and we found that the reason for this is that AXI DMA had
unexpectedly processed a partially updated tail descriptor pointer. To
fix it, we suggest that the driver should use one 64-bit write instead
of two 32-bit writes to perform such update if possible. For those
archectures where double-word load/stores are unavailable, e.g. 32-bit
archectures, force a driver probe failure if the driver finds 64-bit
capability on DMA.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>