libxl: Print device_kind as a string

Printing the integer isn't particularly informative.  Switch to a
human-readable string when printing the device_kind in
libxl__get_hotplug_script_info().

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>

tools/libs/light/libxl_linux.c

@@ -231,8 +231,8 @@ int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
         break;
     default:
         /* No need to execute any hotplug scripts */
-        LOGD(DEBUG, dev->domid,
-             "backend_kind %d, no need to execute scripts", dev->backend_kind);
+        LOGD(DEBUG, dev->domid, "backend_kind %s, no need to execute scripts",
+             libxl__device_kind_to_string(dev->backend_kind));
         rc = 0;
         break;
     }