mtd: nand: atmel: fix of_irq_get() error check

of_irq_get() may return 0 as well as negative error number on failure,
while the driver only checks for the negative values. The driver would
then call devm_request_irq() for IRQ0  in its probe method and never get
a valid interrupt.

Check for 'nc->irq <= 0' instead and return -ENXIO from the driver's probe
if of_irq_get() returned 0.

Fixes: f88fc122cc34 ("mtd: nand: Cleanup/rework the atmel_nand driver")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Wenyou Yang <Wenyou.yang@microchip.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

drivers/mtd/nand/atmel/nand-controller.c

@@ -2078,8 +2078,8 @@ atmel_hsmc_nand_controller_legacy_init(struct atmel_hsmc_nand_controller *nc)
 	}
 
 	nc->irq = of_irq_get(nand_np, 0);
-	if (nc->irq < 0) {
-		ret = nc->irq;
+	if (nc->irq <= 0) {
+		ret = nc->irq ?: -ENXIO;
 		if (ret != -EPROBE_DEFER)
 			dev_err(dev, "Failed to get IRQ number (err = %d)\n",
 				ret);
@@ -2168,11 +2168,12 @@ atmel_hsmc_nand_controller_init(struct atmel_hsmc_nand_controller *nc)
 
 	nc->irq = of_irq_get(np, 0);
 	of_node_put(np);
-	if (nc->irq < 0) {
-		if (nc->irq != -EPROBE_DEFER)
+	if (nc->irq <= 0) {
+		ret = nc->irq ?: -ENXIO;
+		if (ret != -EPROBE_DEFER)
 			dev_err(dev, "Failed to get IRQ number (err = %d)\n",
-				nc->irq);
-		return nc->irq;
+				ret);
+		return ret;
 	}
 
 	np = of_parse_phandle(dev->of_node, "atmel,nfc-io", 0);