xhci-platform: Change compatible string from xhci-platform to generic-xhci

This brings the xhci-platform bindings in sync with what we've done for
the ohci- and ehci-platform drivers. As discussed there using platform as a
postfix is a bit weird as the platform bus is a Linux specific thing and
the bindings are supposed to be OS agnostic.

Note that the old xhci-platform compatible string is kept around for, well,
compatibility reasons.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

 USB xHCI controllers
 
 Required properties:
-  - compatible: should be "xhci-platform".
+  - compatible: should be "generic-xhci" (deprecated: "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";
+		compatible = "generic-xhci";
 		reg = <0xf0931000 0x8c8>;
 		interrupts = <0x0 0x4e 0x0>;
 	};

drivers/usb/host/xhci-plat.c

@@ -226,6 +226,7 @@ static const struct dev_pm_ops xhci_plat_pm_ops = {
 
 #ifdef CONFIG_OF
 static const struct of_device_id usb_xhci_of_match[] = {
+	{ .compatible = "generic-xhci" },
 	{ .compatible = "xhci-platform" },
 	{ },
 };