[media] VPU: mediatek: fix return value check in mtk_vpu_probe()

In case of error, the function devm_clk_get() returns ERR_PTR()
and not returns NULL. The NULL test in the return value check
should be replaced with IS_ERR().
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/mtk-vpu/mtk_vpu.c

@@ -788,9 +788,9 @@ static int mtk_vpu_probe(struct platform_device *pdev)
 
 	/* Get VPU clock */
 	vpu->clk = devm_clk_get(dev, "main");
-	if (!vpu->clk) {
+	if (IS_ERR(vpu->clk)) {
 		dev_err(dev, "get vpu clock failed\n");
-		return -EINVAL;
+		return PTR_ERR(vpu->clk);
 	}
 
 	platform_set_drvdata(pdev, vpu);