USB: serial: use IS_ENABLED() instead of checking for FOO || FOO_MODULE

The IS_ENABLED() macro checks if a Kconfig symbol has been enabled either
built-in or as a module, use that macro instead of open coding the same.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/usb-serial.c

@@ -815,7 +815,7 @@ static int usb_serial_probe(struct usb_interface *interface,
 		}
 	}
 
-#if defined(CONFIG_USB_SERIAL_PL2303) || defined(CONFIG_USB_SERIAL_PL2303_MODULE)
+#if IS_ENABLED(CONFIG_USB_SERIAL_PL2303)
 	/* BEGIN HORRIBLE HACK FOR PL2303 */
 	/* this is needed due to the looney way its endpoints are set up */
 	if (((le16_to_cpu(dev->descriptor.idVendor) == PL2303_VENDOR_ID) &&