VMXNET3: Add support for virtual IOMMU

This patch adds support for virtual IOMMU to the vmxnet3 module.  We
switch to DMA consistent mappings for anything we pass to the device.
There were a few places where we already did this, but using pci_blah();
these have been fixed to use dma_blah(), along with all new occurrences
where we've replaced kmalloc() and friends.

Also fix two small bugs:
1) use after free of rq->buf_info in vmxnet3_rq_destroy()
2) a cpu_to_le32() that should have been a cpu_to_le64()

Acked-by: George Zhang <georgezhang@vmware.com>
Acked-by: Aditya Sarwade <asarwade@vmware.com>
Signed-off-by: Andy King <acking@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>