PCI: rcar: Consolidate register space lookup and ioremap

Move the devm_ioremap_resource() of R-Car register space next to the
of_address_to_resource() that extracts the resource.  No functional change
intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>