PCI: mvebu: Adapt to the new device tree layout

The new device tree layout encodes the window's target ID and attribute
in the PCIe controller node's ranges property. This allows to parse
such entries to obtain such information and use the recently introduced
MBus API to create the windows, instead of using the current name based
scheme.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>