sound/oss/dmasound: fix 'dmasound_setup' defined but not used

stable inclusion
from stable-v5.10.180
commit c820c05c5ff6613ad424dce1cddc459ffd2fb96b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8DDFN

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c820c05c5ff6613ad424dce1cddc459ffd2fb96b



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commit 357ad4d8 upstream.

We observed: 'dmasound_setup' defined but not used error with
COMPILER=gcc ARCH=m68k DEFCONFIG=allmodconfig build.

Fix it by adding __maybe_unused to dmasound_setup.

Error(s):
sound/oss/dmasound/dmasound_core.c:1431:12: error: 'dmasound_setup' defined but not used [-Werror=unused-function]

Fixes: 9dd7c463 ("sound/oss/dmasound: fix build when drivers are mixed =y/=m")
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20220414091940.2216-1-miles.chen@mediatek.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>