net: dwc_eth_qos: Adapt probe() for PCI devices

PCI devices do not necessarily use a device tree. In that case, the
driver currently fails to find eqos->config and eqos->regs.

This commit factors out the respective functionality. Device tree usage
remains default, but board specific implementations will be possible as
well.

Signed-off-by: Philip Oberfichtner <pro@denx.de>
diff --git a/drivers/net/dwc_eth_qos_stm32.c b/drivers/net/dwc_eth_qos_stm32.c
index cffaa10..f3a973f 100644
--- a/drivers/net/dwc_eth_qos_stm32.c
+++ b/drivers/net/dwc_eth_qos_stm32.c
@@ -234,6 +234,12 @@
 
 	interface = eqos->config->interface(dev);
 
+	ret = eqos_get_base_addr_dt(dev);
+	if (ret) {
+		dev_err(dev, "eqos_get_base_addr_dt failed: %d\n", ret);
+		return ret;
+	}
+
 	if (interface == PHY_INTERFACE_MODE_NA) {
 		dev_err(dev, "Invalid PHY interface\n");
 		return -EINVAL;