PCI: rcar: Reuse generic pci_parse_request_of_pci_ranges() function

The non-functional change removes a custom function to parse and
allocate PCI resources in favour of pci_parse_request_of_pci_ranges().

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>