component/bt: legacy bt API provide

1. move btif module out of bluetooth stack
2. provide new APIs in bluedroid/stack_api

components/bt/bluedroid/stack_api/include/bt_gap_api.h

@@ -0,0 +1,33 @@
+#ifndef __BT_GAP_API_H__
+#define __BT_GAP_API_H__
+
+#include <stdint.h>
+
+#include "esp_err.h"
+#include "bt_api_common.h"
+
+/*
+#define ESP_OK         0
+#define ESP_FAIL       -1
+#define ESP_ERR_NO_MEM              0x101
+#define ESP_ERR_INVALID_ARG         0x102
+#define ESP_ERR_INVALID_STATE       0x103
+#define ESP_ERR_INVALID_SIZE        0x104
+#define ESP_ERR_NOT_FOUND           0x105
+*/
+
+#define ESP_ERR_BT_GAP_BASE             (0xf000)       // TODO: move base address to esp_err.h
+// #define ESP_ERR_BT_GAP_XXXX            (ESP_ERR_BT_GAP_BASE + 0xYY)
+
+#define ESP_ERR_BT_SDP_BASE             (0xf100)       // TODO: move base address to esp_err.h
+
+enum {
+    BT_SCAN_MODE_NONE,
+    BT_SCAN_MODE_CONNECTABLE,
+    BT_SCAN_MODE_CONNECTABLE_DISCOVERABLE
+}; // enumerations of bt_scan_mode_t
+typedef uint16_t bt_scan_mode_t;
+
+esp_err_t esp_bt_gap_set_scan_mode(bt_scan_mode_t mode);
+
+#endif /* __BT_GAP_API_H__ */