NTB: Revert the change to use the NTB device dev for DMA allocations

Commit 417cf39c ("NTB: Set dma mask and dma coherent mask to NTB
devices") started using the NTB device for DMA allocations which was
turns out was wrong. If the IOMMU is enabled, such alloctanions will
always fail with messages such as:

  DMAR: Allocating domain for 0000:02:00.1 failed

This is because the IOMMU has not setup the device for such use.

Change the tools back to using the PCI device for allocations seeing
it doesn't make sense to add an IOMMU group for the non-physical NTB
device. Also remove the code that sets the DMA mask as it no longer
makes sense to do this.

Fixes: 7f46c8b3 ("NTB: ntb_tool: Add full multi-port NTB API support")
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Tested-by: Alexander Fomichev <fomichev.ru@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>