sound: restore MultiSound script

This script is mentioned at multisound Kconfig and files. As the
driver still exists, it probably makes sense to restore it.

Fixes: 727dede0 ("sound: Retire OSS")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>