PCI: Constify pci_register_io_range() fwnode_handle

pci_register_io_range() does not modify the passed in fwnode_handle, so
make it const.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20241010-dt-const-v1-1-87a51f558425@kernel.org


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>