PCI: Consolidate PCI DMA constants and interfaces in linux/pci-dma-compat.h

Christoph added a generic include/linux/pci-dma-compat.h, so now there's
one place with most of the PCI DMA interfaces.  Move more PCI DMA-related
things there:

  - The PCI_DMA_* direction constants from linux/pci.h
  - The pci_set_dma_max_seg_size() and pci_set_dma_seg_boundary()
    CONFIG_PCI implementations from drivers/pci/pci.c
  - The pci_set_dma_max_seg_size() and pci_set_dma_seg_boundary()
    !CONFIG_PCI stubs from linux/pci.h
  - The pci_set_dma_mask() and pci_set_consistent_dma_mask()
    !CONFIG_PCI stubs from linux/pci.h

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>