greybus: arche-apb: NULL is a valid regulator

Since NULL could in theory be a valid regulator we ought to check for
IS_ERR() rather than for NULL. In practice this is unlikely to be an
issue but it's better for neatness.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/arche-apb-ctrl.c

@@ -170,14 +170,14 @@ static int apb_ctrl_init_seq(struct platform_device *pdev,
 	}
 
 	/* Enable power to APB */
-	if (apb->vcore) {
+	if (!IS_ERR(apb->vcore)) {
 		ret = regulator_enable(apb->vcore);
 		if (ret) {
 			dev_err(dev, "failed to enable core regulator\n");
 			return ret;
 		}
 	}
-	if (apb->vio) {
+	if (!IS_ERR(apb->vio)) {
 		ret = regulator_enable(apb->vio);
 		if (ret) {
 			dev_err(dev, "failed to enable IO regulator\n");
@@ -246,16 +246,12 @@ static int apb_ctrl_get_devtree_data(struct platform_device *pdev,
 
 	/* Regulators are optional, as we may have fixed supply coming in */
 	apb->vcore = devm_regulator_get(dev, "vcore");
-	if (IS_ERR(apb->vcore)) {
+	if (IS_ERR(apb->vcore))
 		dev_info(dev, "no core regulator found\n");
-		apb->vcore = NULL;
-	}
 
 	apb->vio = devm_regulator_get(dev, "vio");
-	if (IS_ERR(apb->vio)) {
+	if (IS_ERR(apb->vio))
 		dev_info(dev, "no IO regulator found\n");
-		apb->vio = NULL;
-	}
 
 	apb->pinctrl = devm_pinctrl_get(&pdev->dev);
 	if (IS_ERR(apb->pinctrl)) {
@@ -275,10 +271,10 @@ static void apb_ctrl_cleanup(struct arche_apb_ctrl_drvdata *apb)
 {
 	unsigned long flags;
 
-	if (apb->vcore && regulator_is_enabled(apb->vcore) > 0)
+	if (!IS_ERR(apb->vcore) && regulator_is_enabled(apb->vcore) > 0)
 		regulator_disable(apb->vcore);
 
-	if (apb->vio && regulator_is_enabled(apb->vio) > 0)
+	if (!IS_ERR(apb->vio) && regulator_is_enabled(apb->vio) > 0)
 		regulator_disable(apb->vio);
 
 	spin_lock_irqsave(&apb->lock, flags);