components/bt: Add a detailed description for the user to distinguish the function of the query buffer api.

components/bt/host/bluedroid/api/esp_gatt_common_api.c

@@ -53,7 +53,7 @@ extern UINT16 L2CA_GetFreePktBufferNum_LE(void);
 
 /**
  * @brief           This function is called to get currently sendable packets number on controller,
- *                  the function is called only in BLE running core now.
+ *                  the function is called only in BLE running core and single connection now.
  *
  * @return
  *                  sendable packets number on controller
@@ -65,6 +65,15 @@ uint16_t esp_ble_get_sendable_packets_num (void)
     return L2CA_GetFreePktBufferNum_LE();
 }
 
+/**
+ * @brief           This function is used to query the number of available buffers for the current connection.
+ *                  When you need to query the current available buffer number, it is recommended to use this API.
+ * @param[in]       conn_id: current connection id.
+ * 
+ * @return
+ *                  Number of available buffers for the current connection
+ *
+ */
  
 extern UINT16 L2CA_GetCurFreePktBufferNum_LE(UINT16 conn_id);
 uint16_t esp_ble_get_cur_sendable_packets_num (uint16_t connid)