Input: Add DeleteInputDeviceRequest

Add DIDR, which asks the DDX to remove a device, analogous to
NewInputDeviceRequest.  Only implemented for XFree86 at the moment.

hw/kdrive/src/kinput.c

@@ -2374,3 +2374,8 @@ NewInputDeviceRequest(InputOption *options)
 
     return Success;
 }
+
+void
+DeleteInputDeviceRequest(DeviceIntPtr pDev)
+{
+}