PCI: Unify pci_resource_to_user() declarations

Replace the pci_resource_to_user() declarations in each arch that defines
HAVE_ARCH_PCI_RESOURCE_TO_USER with a single one in linux/pci.h.

Change the MIPS static inline implementation to a non-inline version so the
static inline doesn't conflict with the new non-static linux/pci.h
declaration.

No functional change intended.

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