mtdconfig/nvs: return 0 when delete a non-exist kv

Deleting a non-existent key-value pair is deemed a successful deletion.

Signed-off-by: zhaoxingyu1 <zhaoxingyu1@xiaomi.com>

drivers/mtd/mtd_config_nvs.c

@@ -1923,7 +1923,7 @@ static ssize_t nvs_write(FAR struct nvs_fs *fs,
 
       if (pdata->len == 0)
         {
-          return -ENOENT;
+          return 0;
         }
     }