PCI: rcar: Add Gen2 PHY setup to pcie-rcar

For PCIe compliance, the PHY registers need setting as per the manual.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>