freertos/xt_asm_utils: added documentation of current windows spill solution

components/freertos/xt_asm_utils.h

@@ -1,3 +1,28 @@
+/* Copyright 2015-2018 Espressif Systems (Shanghai) PTE LTD
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* File adapted to use on IDF FreeRTOS component, extracted 
+ * originally from zephyr RTOS code base
+ */
+
+/*
+ * Copyright (c) 2017, Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 #ifndef __XT_ASM_UTILS_H
 #define __XT_ASM_UTILS_H
 
@@ -59,5 +84,4 @@
 #endif
 .endm
 
-
 #endif