HSI: omap_ssi_port: fix handling of_get_named_gpio result

The function can return negative value.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/hsi/controllers/omap_ssi_port.c

@@ -1147,13 +1147,13 @@ static int __init ssi_port_probe(struct platform_device *pd)
 		goto error;
 	}
 
-	cawake_gpio = of_get_named_gpio(np, "ti,ssi-cawake-gpio", 0);
-	if (cawake_gpio < 0) {
+	err = of_get_named_gpio(np, "ti,ssi-cawake-gpio", 0);
+	if (err < 0) {
 		dev_err(&pd->dev, "DT data is missing cawake gpio (err=%d)\n",
-			cawake_gpio);
-		err = -ENODEV;
+			err);
 		goto error;
 	}
+	cawake_gpio = err;
 
 	err = devm_gpio_request_one(&port->device, cawake_gpio, GPIOF_DIR_IN,
 		"cawake");