ALSA: ctxfi: Fix potential OOB access in audio mixer handling

In the audio mixer handling code of ctxfi driver, the conf field is
used as a kind of loop index, and it's referred in the index callbacks
(amixer_index() and sum_index()).

As spotted recently by fuzzers, the current code causes OOB access at
those functions.
| UBSAN: array-index-out-of-bounds in /build/reproducible-path/linux-6.17.8/sound/pci/ctxfi/ctamixer.c:347:48
| index 8 is out of range for type 'unsigned char [8]'

After the analysis, the cause was found to be the lack of the proper
(re-)initialization of conj field.

This patch addresses those OOB accesses by adding the proper
initializations of the loop indices.

Reported-by: Salvatore Bonaccorso <carnil@debian.org>
Tested-by: Karsten Hohmeier <linux@hohmatik.de>
Closes: https://bugs.debian.org/1121535
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/all/aSk8KJI35H7gFru6@eldamar.lan/
Link: https://patch.msgid.link/20260119133212.189129-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: tiwai

sound/pci/ctxfi/ctamixer.c

@@ -205,6 +205,7 @@ static int amixer_rsc_init(struct amixer *amixer,
 
 	/* Set amixer specific operations */
 	amixer->rsc.ops = &amixer_basic_rsc_ops;
+	amixer->rsc.conj = 0;
 	amixer->ops = &amixer_ops;
 	amixer->input = NULL;
 	amixer->sum = NULL;
@@ -367,6 +368,7 @@ static int sum_rsc_init(struct sum *sum,
 		return err;
 
 	sum->rsc.ops = &sum_basic_rsc_ops;
+	sum->rsc.conj = 0;
 
 	return 0;
 }