PCI: v3: Update the device tree bindings

The bindings for the V3 Semiconductor PCI bridge are a tad bit outdated and
predates the more formal format we have adopted for the bindings.

Update them a bit so it is easier to read, and add the Integrator AP-
specific compatible so we can detect that we are running on that specific
platform.

Add a second register bank for the configuration memory area. The device
tree specs do specify a memory range for configuration space but it is not
applicable to custom accessors like this. Instead follow the pattern from
the Versatile PCI adapter and simply add a second register bank for this
memory.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>