e1000, e1000e: Use dma_rmb instead of rmb for descriptor read ordering

This change replaces calls to rmb with dma_rmb in the case where we want to
order all follow-on descriptor reads after the check for the descriptor
status bit.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>