staging: drm/imx: fix return value check in ipu_add_subdevice_pdata()

In case of error, the function platform_device_register_data() returns
ERR_PTR() and never returns NULL. The NULL test in the return value check
should be replaced with IS_ERR().
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/imx-drm/ipu-v3/ipu-common.c

@@ -1006,7 +1006,7 @@ static int ipu_add_subdevice_pdata(struct device *dev,
 	pdev = platform_device_register_data(dev, reg->name, ipu_client_id++,
 			&reg->pdata, sizeof(struct ipu_platform_reg));
 
-	return pdev ? 0 : -EINVAL;
+	return PTR_ERR_OR_ZERO(pdev);
 }
 
 static int ipu_add_client_devices(struct ipu_soc *ipu)