ALSA: ctxfi: Keep line/mic notification controls per mixer

ALSA: ctxfi: Keep line/mic notification controls per mixer

ctxfi stores the Line Capture Switch and Mic Capture Switch controls in
a file-scope kctls[] array so do_line_mic_switch() can notify the
opposite control when the shared line/mic input selection changes.

That storage is shared by all ctxfi cards. If more than one X-Fi card is
present, a later card can overwrite the pointers saved by an earlier one.
A control update on one card can then use another card's kcontrol object
for snd_ctl_notify(). If that other card is removed, the saved pointer can
also become stale.

Store those notification targets in struct ct_mixer instead. The mixer is
per-card state and matches the lifetime of the controls created for that
card.

Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
Link: https://patch.msgid.link/20260517-alsa-ctxfi-mixer-kctls-v1-1-6e4f81f6b658@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>