usb: Add Device Tree support to XHCI Platform driver

Add Device Tree match table to xhci-plat.c. Add DT bindings document.
Signed-off-by: Al Cooper <alcooperx@gmail.com>
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

Documentation/devicetree/bindings/usb/usb-xhci.txt

+USB xHCI controllers
+
+Required properties:
+  - compatible: should be "xhci-platform".
+  - reg: should contain address and length of the standard XHCI
+    register set for the device.
+  - interrupts: one XHCI interrupt should be described here.
+
+Example:
+	usb@f0931000 {
+		compatible = "xhci-platform";
+		reg = <0xf0931000 0x8c8>;
+		interrupts = <0x0 0x4e 0x0>;
+	};

drivers/usb/host/xhci-plat.c

@@ -14,6 +14,7 @@
 #include <linux/platform_device.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/of.h>
 
 #include "xhci.h"
 
@@ -211,12 +212,21 @@ static const struct dev_pm_ops xhci_plat_pm_ops = {
 #define DEV_PM_OPS	NULL
 #endif /* CONFIG_PM */
 
+#ifdef CONFIG_OF
+static const struct of_device_id usb_xhci_of_match[] = {
+	{ .compatible = "xhci-platform" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, usb_xhci_of_match);
+#endif
+
 static struct platform_driver usb_xhci_driver = {
 	.probe	= xhci_plat_probe,
 	.remove	= xhci_plat_remove,
 	.driver	= {
 		.name = "xhci-hcd",
 		.pm = DEV_PM_OPS,
+		.of_match_table = of_match_ptr(usb_xhci_of_match),
 	},
 };
 MODULE_ALIAS("platform:xhci-hcd");