global: Migrate CONFIG_FEC_MXC_PHYADDR to CFG

Perform a simple rename of CONFIG_FEC_MXC_PHYADDR to CFG_FEC_MXC_PHYADDR

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c
index 9cb235a..ab52cc1 100644
--- a/drivers/net/fec_mxc.c
+++ b/drivers/net/fec_mxc.c
@@ -1086,8 +1086,8 @@
 	int addr;
 
 	addr = device_get_phy_addr(priv, dev);
-#ifdef CONFIG_FEC_MXC_PHYADDR
-	addr = CONFIG_FEC_MXC_PHYADDR;
+#ifdef CFG_FEC_MXC_PHYADDR
+	addr = CFG_FEC_MXC_PHYADDR;
 #endif
 
 	phydev = phy_connect(priv->bus, addr, dev, priv->interface);