USB: fix build error with CONFIG_PM_RUNTIME disabled

commit bdd405d2a528 ("usb: hub: Prevent hub autosuspend if
usbcore.autosuspend is -1") causes a build error if CONFIG_PM_RUNTIME is
disabled.  Fix that by doing a simple #ifdef guard around it.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Roger Quadros <rogerq@ti.com>
Cc: Michael Welling <mwelling@emacinc.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hub.c

@@ -1732,8 +1732,10 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
 	 * - If user has indicated to prevent autosuspend by passing
 	 *   usbcore.autosuspend = -1 then keep autosuspend disabled.
 	 */
+#ifdef CONFIG_PM_RUNTIME
 	if (hdev->dev.power.autosuspend_delay >= 0)
 		pm_runtime_set_autosuspend_delay(&hdev->dev, 0);
+#endif
 
 	/*
 	 * Hubs have proper suspend/resume support, except for root hubs