The ibm p7 architecure seems to reorder memory accesses more
aggressively than previous ppc64 architectures. This requires memory
barriers to ensure that rx/tx doorbells are pressed only after
memory to be DMAed is written.
Signed-off-by: NSathya Perla <sathyap@serverengines.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>