usb: chipidea: msm: get optional clock by devm_clk_get_optional()

When the driver tries to get optional clock, it ignores all errors except
-EPROBE_DEFER, but if only ignores -ENOENT, it will cover some real errors,
such as -ENOMEM, so use devm_clk_get_optional() to get optional clock.

Cc: Peter Chen <Peter.Chen@nxp.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: Peter Chen <Peter.Chen@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/chipidea/ci_hdrc_msm.c

@@ -205,12 +205,9 @@ static int ci_hdrc_msm_probe(struct platform_device *pdev)
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
 
-	ci->fs_clk = clk = devm_clk_get(&pdev->dev, "fs");
-	if (IS_ERR(clk)) {
-		if (PTR_ERR(clk) == -EPROBE_DEFER)
-			return -EPROBE_DEFER;
-		ci->fs_clk = NULL;
-	}
+	ci->fs_clk = clk = devm_clk_get_optional(&pdev->dev, "fs");
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 	ci->base = devm_ioremap_resource(&pdev->dev, res);