MAINTAINERS: add missing maintainers for Simple Audio Card

Mark Brown will take the patch. Add his name.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://patch.msgid.link/87v7uqkpye.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>