hwspinlock: Fix incorrect return pointers

The commit 4f1acd75 ("hwspinlock: Add devm_xxx() APIs to request/free
hwlock") introduces one bug, that will return one error pointer if failed
to request one hwlock, but we expect NULL pointer on error for consumers.
This patch will fix this issue.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NBaolin Wang <baolin.wang@linaro.org>
Signed-off-by: NBjorn Andersson <bjorn.andersson@linaro.org>

drivers/hwspinlock/hwspinlock_core.c

@@ -877,10 +877,10 @@ struct hwspinlock *devm_hwspin_lock_request(struct device *dev)
 
 	ptr = devres_alloc(devm_hwspin_lock_release, sizeof(*ptr), GFP_KERNEL);
 	if (!ptr)
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 
 	hwlock = hwspin_lock_request();
-	if (!IS_ERR(hwlock)) {
+	if (hwlock) {
 		*ptr = hwlock;
 		devres_add(dev, ptr);
 	} else {
@@ -913,10 +913,10 @@ struct hwspinlock *devm_hwspin_lock_request_specific(struct device *dev,
 
 	ptr = devres_alloc(devm_hwspin_lock_release, sizeof(*ptr), GFP_KERNEL);
 	if (!ptr)
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 
 	hwlock = hwspin_lock_request_specific(id);
-	if (!IS_ERR(hwlock)) {
+	if (hwlock) {
 		*ptr = hwlock;
 		devres_add(dev, ptr);
 	} else {