tools(unit-test-app): Modify for ESP8266

1. Remove unused or unsupported unit test
2. Add extra header file to pass compiling
3. Remove unsupported functions

components/esp8266/include/esp_clk.h

@@ -0,0 +1,25 @@
+// Copyright 2015-2017 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.
+
+#pragma once
+
+/**
+ * @brief Return current CPU clock frequency
+ * When frequency switching is performed, this frequency may change.
+ * However it is guaranteed that the frequency never changes with a critical
+ * section.
+ *
+ * @return CPU clock frequency, in Hz
+ */
+int esp_clk_cpu_freq(void);