The Cortina Gemini has an internal PCI root bus, add this to
the device tree, and add interrupt mapping (swizzling) to the
relevant systems device trees.

Cc: Janos Laube <janos.dev@gmail.com>
Cc: Paulius Zaleckas <paulius.zaleckas@gmail.com>
Cc: Hans Ulli Kroll <ulli.kroll@googlemail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Feng-Hsin Chiang <john453@faraday-tech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>