PCI: Move multiple declarations of pci_mmap_page_range() to <linux/pci.h>

We can declare it <linux/pci.h> even on platforms where it isn't going to
be defined.  There's no need to have it littered through the various
<asm/pci.h> files.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>