fix wimax

Change-Id: Ieff7638293e01546baf382d9c8a5b798cff46331
diff --git a/nandroid.c b/nandroid.c
index d49cbab..f1564dc 100644
--- a/nandroid.c
+++ b/nandroid.c
@@ -316,7 +316,7 @@
         else
         {
             ui_print("Erasing WiMAX before restore...\n");
-            if (0 != (ret = format_device("wimax")))
+            if (0 != (ret = format_volume("/wimax")))
                 return print_and_error("Error while formatting wimax!\n");
             ui_print("Restoring WiMAX image...\n");
             if (0 != (ret = restore_raw_partition("wimax", tmp)))