ALSA: aoa: Fix I2S device accounting

i2sbus_add_dev() is supposed to return the number of probed devices,
i.e. either 1 or 0.  However, i2sbus_add_dev() has one error handling
that returns -ENODEV; this will screw up the accumulation number
counted in the caller, i2sbus_probe().

Fix the return value to 0 and add the comment for better understanding
for readers.

Fixes: f3d9478b ("[ALSA] snd-aoa: add snd-aoa")
Link: https://lore.kernel.org/r/20221027065233.13292-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/aoa/soundbus/i2sbus/core.c

@@ -147,6 +147,7 @@ static int i2sbus_get_and_fixup_rsrc(struct device_node *np, int index,
 	return rc;
 }
 
+/* Returns 1 if added, 0 for otherwise; don't return a negative value! */
 /* FIXME: look at device node refcounting */
 static int i2sbus_add_dev(struct macio_dev *macio,
 			  struct i2sbus_control *control,
@@ -213,7 +214,7 @@ static int i2sbus_add_dev(struct macio_dev *macio,
 	 * either as the second one in that case is just a modem. */
 	if (!ok) {
 		kfree(dev);
-		return -ENODEV;
+		return 0;
 	}
 
 	mutex_init(&dev->lock);