ALSA: control: Introduce snd_ctl_find_id_mixer_locked()

Adds wrapper function snd_ctl_find_id_mixer_locked(). This is
identical to snd_ctl_find_id_mixer() except that it can be called
from code that is already holding controls_rwsem.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Link: https://msgid.link/r/20240401100210.61277-2-rf@opensource.cirrus.com


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