PCI: Remove pci_unmap_addr() wrappers for DMA API

Only some of these were still used by the cxgb4 driver, and that despite
the fact that the driver otherwise uses the generic DMA API.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>