thermal: spear13xx: checking for NULL instead of IS_ERR()

thermal_zone_device_register() never returns NULL, on error it returns and
ERR_PTR().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Viresh Kumar <viresh.kumar@st.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@st.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/thermal/spear_thermal.c

@@ -149,9 +149,9 @@ static int spear_thermal_probe(struct platform_device *pdev)
 
 	spear_thermal = thermal_zone_device_register("spear_thermal", 0,
 				stdev, &ops, 0, 0, 0, 0);
-	if (!spear_thermal) {
+	if (IS_ERR(spear_thermal)) {
 		dev_err(&pdev->dev, "thermal zone device is NULL\n");
-		ret = -EINVAL;
+		ret = PTR_ERR(spear_thermal);
 		goto disable_clk;
 	}