usb: renesas_usbhs: Kconfig: convert to SPDX identifiers

By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/renesas_usbhs/Kconfig

+# SPDX-License-Identifier: GPL-2.0
 #
 # Renesas USBHS Controller Drivers
 #