net: ethernet: ixp4xx: Add error handling in ixp4xx_eth_probe()

The function ixp4xx_eth_probe() does not perform sufficient error
checking after executing devm_ioremap_resource(), which can result
in crashes if a critical error path is encountered.

Fixes: f458ac47 ("ARM/net: ixp4xx: Pass ethernet physical base as resource")
Signed-off-by: NZhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: NTang Bin <tangbin@cmss.chinamobile.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/xscale/ixp4xx_eth.c

@@ -1387,6 +1387,8 @@ static int ixp4xx_eth_probe(struct platform_device *pdev)
 		return -ENODEV;
 	regs_phys = res->start;
 	port->regs = devm_ioremap_resource(dev, res);
+	if (IS_ERR(port->regs))
+		return PTR_ERR(port->regs);
 
 	switch (port->id) {
 	case IXP4XX_ETH_NPEA: