wifi_files: Fix file descriptor leak

b/25661479

Change-Id: Ib2da312f59bea93ef5b4e7de8563c8089c360760
diff --git a/cmds/wifi_files.c b/cmds/wifi_files.c
index b25e573..1d95683 100644
--- a/cmds/wifi_files.c
+++ b/cmds/wifi_files.c
@@ -609,6 +609,8 @@
     char buf[24];
     if (fgets(buf, sizeof(buf), fptr) != NULL)
       fprintf(wifi_show_handle, "  \"AutoType\": \"%s\"\n", buf);
+    fclose(fptr);
+    fptr = NULL;
   }
   fprintf(wifi_show_handle, "}\n");