drivers: net: xgene: Fix crash on DT systems

On DT systems the driver require a clock, but the probe just print a
warning and continue, leading to a crash when resetting the device.
To fix this crash and properly handle probe deferals only ignore the
missing clock if DT isn't used or if the clock doesn't exist.
Signed-off-by: Alban Bedel <alban.bedel@avionic-design.de>
Acked-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/apm/xgene/xgene_enet_main.c

@@ -1749,6 +1749,12 @@ static int xgene_enet_get_resources(struct xgene_enet_pdata *pdata)
 
 	pdata->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(pdata->clk)) {
+		/* Abort if the clock is defined but couldn't be retrived.
+		 * Always abort if the clock is missing on DT system as
+		 * the driver can't cope with this case.
+		 */
+		if (PTR_ERR(pdata->clk) != -ENOENT || dev->of_node)
+			return PTR_ERR(pdata->clk);
 		/* Firmware may have set up the clock already. */
 		dev_info(dev, "clocks have been setup already\n");
 	}