ARM: Kirkwood: ehci-orion: Add device tree binding

Based on previous work by Michael Walle and Jason Cooper.

Made their work actually work, which required added interrupt from DT
and auxdata, along with setting the dma_mask, which DT does not
currently do.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

Documentation/devicetree/bindings/usb/ehci-orion.txt

@@ -0,0 +1,15 @@
+* EHCI controller, Orion Marvell variants
+
+Required properties:
+- compatible: must be "marvell,orion-ehci"
+- reg: physical base address of the controller and length of memory mapped
+  region.
+- interrupts: The EHCI interrupt
+
+Example:
+
+	ehci@50000 {
+		compatible = "marvell,orion-ehci";
+		reg = <0x50000 0x1000>;
+		interrupts = <19>;
+	};