ASoC: ak4613: tidyup vendor prefix from ak4613 to asahi-kasei

a3af0c65("ASoC: ak4613: add single-end optional property for IN/OUT pins")
added IN/OUT pin single-end optional property, but it used "ak4613" as
vendor prefix. This patch fixup to asahi-kasei.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>