dt-bindings: PCI: rcar: Correct example to match reality

Correct the USB subnodes in the example, as in f7d569c1 ("ARM: dts:
r8a779x: Fix PCI bus dtc warnings").
  1. Drop the bogus 'device_type = "pci"' properties,
  2. Correct the unit addresses.

Update other bits in the example to match real use:
  1. Rename the USB subnodes from "pci" to "usb",
  2. Update the "phys" property.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Rob Herring <robh@kernel.org>