Some architectures do not have a simple view of the PCI I/O space and
instead use a range of CPU addresses that map to bus addresses.  For some
architectures these ranges will be expressed by OF bindings in a device
tree file.

This patch introduces a pci_register_io_range() helper function with a
generic implementation that can be used by such architectures to keep track
of the I/O ranges described by the PCI bindings.  If the PCI_IOBASE macro
is not defined, that signals lack of support for PCI and we return an
error.

In order to retrieve the CPU address associated with an I/O port, a new
helper function pci_pio_to_address() is introduced.  This will search in
the list of ranges registered with pci_register_io_range() and return the
CPU address that corresponds to the given port.

[arnd: add dummy !CONFIG_OF pci_pio_to_address() to fix build errors]
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
CC: Grant Likely <grant.likely@linaro.org>