net: mdio-ipq4019: Fix the error for an optional regs resource

The second resource is optional which is only provided on the chipset
IPQ5018. But the blamed commit ignores that and if the resource is
not there it just fails.

the resource is used like this,
	if (priv->eth_ldo_rdy) {
		val = readl(priv->eth_ldo_rdy);
		val |= BIT(0);
		writel(val, priv->eth_ldo_rdy);
		fsleep(IPQ_PHY_SET_DELAY_US);
	}

This patch reverts that to still allow the second resource to be optional
because other SoC have the some MDIO controller and doesn't need to
second resource.

Fixes: fa14d03e ("net: mdio-ipq4019: Make use of devm_platform_ioremap_resource()")
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20210928134849.2092-1-caihuoqing@baidu.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>