e100: fix dma error in direction for mapping

The e100 driver triggers BUG_ON(buf->direction != dir)
by doing pci_map_single(..., PCI_DMA_BIDIRECTIONAL)
and pci_dma_sync_single_for_device(..., PCI_DMA_TODEVICE).

Changing the DMA direction, especially with dmabounce will result
in unexpected behaviour.

Reported-by: Anders Grafstrom <grfstrm@users.sourceforge.net>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>