feat(esp8266): Add phy init data in code

Not support to config phy_init_data now, and need real code to use this data.

components/esp8266/include/esp_phy_init.h

@@ -0,0 +1,37 @@
+// Copyright 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.
+
+#pragma once
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file PHY init parameters and API
+ */
+
+
+/**
+ * @brief Structure holding PHY init parameters
+ */
+typedef struct {
+    uint8_t params[128];                    /*!< opaque PHY initialization parameters */
+} esp_phy_init_data_t;
+
+#ifdef __cplusplus
+}
+#endif
+