ASoC: sh: 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: Mark Brown <broonie@kernel.org>

sound/soc/sh/Kconfig

+# SPDX-License-Identifier: GPL-2.0
 menu "SoC Audio support for Renesas SoCs"
 	depends on SUPERH || ARCH_RENESAS || COMPILE_TEST