cpsw: fix undefined function with PM disabled

When CONFIG_PM is not enabled, the function
davinci_mdio_update_dt_from_phymask is not defined. This patch fixes
this so that the build does not fail with CONFIG_PM disabled.

Signed-off-by: Will Eccles <will@eccles.dev>

drivers/net/ethernet/ti/davinci_mdio.c

@@ -704,6 +704,8 @@ static int davinci_mdio_runtime_resume(struct device *dev)
 	}
 	return 0;
 }
+#endif
+
 static void davinci_mdio_update_dt_from_phymask(u32 phy_mask)
 {
 	int i, len, skip;
@@ -791,7 +793,6 @@ static void davinci_mdio_update_dt_from_phymask(u32 phy_mask)
 		kfree(phy_id_property);
 	}
 }
-#endif
 
 #ifdef CONFIG_PM_SLEEP
 static int davinci_mdio_suspend(struct device *dev)