ALSA: bebob: Use a signed return type for get_formation_index

The return type "unsigned int" was used by the get_formation_index function
despite of the aspect that it will eventually return a negative	error code.
So, change to signed int and get index by reference in the parameters.

Done with the help of Coccinelle.

[Fix the missing braces suggested by Julia Lawall -- tiwai]

Signed-off-by: Lucas Tanure <tanure@linux.com>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Tested-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/bebob/bebob_stream.c

@@ -47,14 +47,16 @@ static const unsigned int bridgeco_freq_table[] = {
 	[6] = 0x07,
 };
 
-static unsigned int
-get_formation_index(unsigned int rate)
+static int
+get_formation_index(unsigned int rate, unsigned int *index)
 {
 	unsigned int i;
 
 	for (i = 0; i < ARRAY_SIZE(snd_bebob_rate_table); i++) {
-		if (snd_bebob_rate_table[i] == rate)
-			return i;
+		if (snd_bebob_rate_table[i] == rate) {
+			*index = i;
+			return 0;
+		}
 	}
 	return -EINVAL;
 }
@@ -425,7 +427,9 @@ make_both_connections(struct snd_bebob *bebob, unsigned int rate)
 		goto end;
 
 	/* confirm params for both streams */
-	index = get_formation_index(rate);
+	err = get_formation_index(rate, &index);
+	if (err < 0)
+		goto end;
 	pcm_channels = bebob->tx_stream_formations[index].pcm;
 	midi_channels = bebob->tx_stream_formations[index].midi;
 	err = amdtp_am824_set_parameters(&bebob->tx_stream, rate,