arm: mvebu: PCIe Device Tree informations for Armada 370 Mirabox

The Globalscale Mirabox platform uses one PCIe interface for an
available mini-PCIe slot, and the other PCIe interface for an internal
USB 3.0 controller. We add the necessary Device Tree informations to
enable those two interfaces.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>