PCI: rcar: Remove unused rcar_pcie_get_resources() platform_device arg

rcar_pcie_get_resources() doesn't use the platform_device pointer passed to
it, so remove it.  No functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>