E100: work around the driver using streaming DMA mapping for RX descriptors.

E100 places it's RX packet descriptors inside skb->data and uses them
with bidirectional streaming DMA mapping. Unfortunately it fails to
transfer skb->data ownership to the device after it reads the
descriptor's status, breaking on non-coherent (e.g., ARM) platforms.

This have to be converted to use coherent memory for the descriptors.

Signed-off-by: Krzysztof Halasa <khc@pm.waw.pl>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>