PCI: rcar-gen2: Convert to use modern host bridge probe functions

The rcar-gen2 host driver still uses the old Arm PCI setup function
pci_common_init_dev(). Let's update it to use the modern
devm_pci_alloc_host_bridge(), pci_parse_request_of_pci_ranges() and
pci_host_probe() functions.

Link: https://lore.kernel.org/r/20200722022514.1283916-18-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-renesas-soc@vger.kernel.org