sungem, sunhme, sunvnet: Update drivers to use dma_wmb/rmb

This patch goes through and replaces wmb/rmb with dma_wmb/dma_rmb in cases
where the barrier is being used to order writes or reads to just memory and
doesn't involve any programmed I/O.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>