forcedeth: replace pci_alloc_consistent with dma_alloc_coherent

The functions pci_alloc_consistent is obsolete. So it is replaced
with dma_alloc_coherent

Signed-off-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>