net: stmmac: dwmac-visconti: Make use of the helper function dev_err_probe()

When possible use dev_err_probe help to properly deal with the
PROBE_DEFER error, the benefit is that DEFER issue will be logged
in the devices_deferred debugfs file.
And using dev_err_probe() can reduce code size, and the error value
gets printed.

Signed-off-by: Cai Huoqing <[e-mail]>
Acked-by: Nobuhiro Iwamatsu <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/stmicro/stmmac/dwmac-visconti.c

···
 	int err;
 
 	dwmac->phy_ref_clk = devm_clk_get(&pdev->dev, "phy_ref_clk");
-	if (IS_ERR(dwmac->phy_ref_clk)) {
-		dev_err(&pdev->dev, "phy_ref_clk clock not found.\n");
-		return PTR_ERR(dwmac->phy_ref_clk);
-	}
+	if (IS_ERR(dwmac->phy_ref_clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(dwmac->phy_ref_clk),
+				     "phy_ref_clk clock not found.\n");
 
 	err = clk_prepare_enable(dwmac->phy_ref_clk);
 	if (err < 0) {