net: mdio-uclass: fix type for phy_mode_str and phy_handle_str

These global variables should both have type
  static const char * const

Signed-off-by: Marek BehĂșn <marek.behun@nic.cz>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
diff --git a/net/mdio-uclass.c b/net/mdio-uclass.c
index e74e34f..5735afe 100644
--- a/net/mdio-uclass.c
+++ b/net/mdio-uclass.c
@@ -17,13 +17,14 @@
 
 /* DT node properties for MAC-PHY interface */
 #define PHY_MODE_STR_CNT	2
-static const char *phy_mode_str[PHY_MODE_STR_CNT] = { "phy-mode",
-						      "phy-connection-type" };
+static const char * const phy_mode_str[PHY_MODE_STR_CNT] = {
+	"phy-mode", "phy-connection-type"
+};
 /* DT node properties that reference a PHY node */
 #define PHY_HANDLE_STR_CNT	3
-const char *phy_handle_str[PHY_HANDLE_STR_CNT] = { "phy-handle",
-						   "phy",
-						   "phy-device" };
+static const char * const phy_handle_str[PHY_HANDLE_STR_CNT] = {
+	"phy-handle", "phy", "phy-device"
+};
 
 void dm_mdio_probe_devices(void)
 {