PCI: rcar: Convert to DT resource parsing API

The main purpose of this change is to avoid calling pci_ioremap_io() as
this is not available on arm64.  However, instead of doing the range
parsing in this driver we can utilise of_pci_get_host_bridge_resources().

This is similar to changes made to the generic PCI host driver in commit
dbf9826d ("PCI: generic: Convert to DT resource parsing API")

Reported-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>