net: fix phy_string_for_interface

commit ffb0f6f488b9 ("treewide: Rename PHY_INTERFACE_MODE_NONE to
PHY_INTERFACE_MODE_NA") broke the phy_string_for_interface function.
Fix it.

Fixes ffb0f6f488b9 ("treewide: Rename PHY_INTERFACE_MODE_NONE to PHY_INTERFACE_MODE_NA")
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Cc: Marek BehĂșn <marek.behun@nic.cz>
Cc: Stefan Roese <sr@denx.de>
Cc: Ramon Fried <rfried.dev@gmail.com>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Marek BehĂșn <marek.behun@nic.cz>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
diff --git a/include/phy_interface.h b/include/phy_interface.h
index ce3b500..fed3357 100644
--- a/include/phy_interface.h
+++ b/include/phy_interface.h
@@ -85,7 +85,7 @@
 static inline const char *phy_string_for_interface(phy_interface_t i)
 {
 	/* Default to unknown */
-	if (i > PHY_INTERFACE_MODE_NA)
+	if (i >= PHY_INTERFACE_MODE_MAX)
 		i = PHY_INTERFACE_MODE_NA;
 
 	return phy_interface_strings[i];