[ALSA] aoa: feature gpio layer: fix IRQ access

The IRQ rework caused some hiccups here, in some cases we call
get_irq without a device node. This patch makes it catch that
case and return NO_IRQ when it happens, along with changing the
place where the irq is checked to check for NO_IRQ instead of -1.
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/aoa/core/snd-aoa-gpio-feature.c b/sound/aoa/core/snd-aoa-gpio-feature.c
index 7ae0c0b..f69d333 100644
--- a/sound/aoa/core/snd-aoa-gpio-feature.c
+++ b/sound/aoa/core/snd-aoa-gpio-feature.c
@@ -112,7 +112,10 @@
 
 static void get_irq(struct device_node * np, int *irqptr)
 {
-	*irqptr = irq_of_parse_and_map(np, 0);
+	if (np)
+		*irqptr = irq_of_parse_and_map(np, 0);
+	else
+		*irqptr = NO_IRQ;
 }
 
 /* 0x4 is outenable, 0x1 is out, thus 4 or 5 */
@@ -322,7 +325,7 @@
 		return -EINVAL;
 	}
 
-	if (irq == -1)
+	if (irq == NO_IRQ)
 		return -ENODEV;
 
 	mutex_lock(&notif->mutex);