dt-bindings: PCI: uniphier: Convert uniphier-pcie.txt to json-schema

Convert the file into a JSON description at the yaml format.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1648617814-9217-2-git-send-email-hayashi.kunihiko@socionext.com