slimbus: fix a potential NULL pointer dereference in of_qcom_slim_ngd_register

In case platform_device_alloc fails, the fix returns an error
code to avoid the NULL pointer dereference.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/slimbus/qcom-ngd-ctrl.c

@@ -1342,6 +1342,10 @@ static int of_qcom_slim_ngd_register(struct device *parent,
 			return -ENOMEM;
 
 		ngd->pdev = platform_device_alloc(QCOM_SLIM_NGD_DRV_NAME, id);
+		if (!ngd->pdev) {
+			kfree(ngd);
+			return -ENOMEM;
+		}
 		ngd->id = id;
 		ngd->pdev->dev.parent = parent;
 		ngd->pdev->driver_override = QCOM_SLIM_NGD_DRV_NAME;