ALSA: ac97bus: Use guard() for mutex locks

ALSA: ac97bus: Use guard() for mutex locks

[ Upstream commit c07824a14d99c10edd4ec4c389d219af336ecf20 ]

Replace the manual mutex lock/unlock pairs with guard() for code
simplification.

Only code refactoring, and no behavior change.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20250829151335.7342-18-tiwai@suse.de
Stable-dep-of: 830988b6cf19 ("ALSA: ac97: fix a double free in snd_ac97_controller_register()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>