docs(ble/bluedroid): Optimize doc for registering BLE callback functions

(cherry picked from commit d84ccadf90)

Co-authored-by: zhanghaipeng <zhanghaipeng@espressif.com>

components/bt/host/bluedroid/api/include/api/esp_gap_ble_api.h

@@ -1593,6 +1593,8 @@ typedef void (* esp_gap_ble_cb_t)(esp_gap_ble_cb_event_t event, esp_ble_gap_cb_p
  *
  * @param[in]       callback: callback function
  *
+ * @note            Avoid performing time-consuming operations within the callback functions.
+ *
  * @return
  *                  - ESP_OK : success
  *                  - other  : failed

components/bt/host/bluedroid/api/include/api/esp_gattc_api.h

@@ -272,6 +272,8 @@ typedef void (* esp_gattc_cb_t)(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_
  *
  * @param[in]      callback The pointer to the application callback function
  *
+ * @note            Avoid performing time-consuming operations within the callback functions.
+ *
  * @return
  *          - ESP_OK: Success
  *          - ESP_FAIL: Failure

components/bt/host/bluedroid/api/include/api/esp_gatts_api.h

@@ -283,6 +283,8 @@ typedef void (* esp_gatts_cb_t)(esp_gatts_cb_event_t event, esp_gatt_if_t gatts_
  *
  * @param[in] callback The pointer to the application callback function
  *
+ * @note            Avoid performing time-consuming operations within the callback functions.
+ *
  * @return
  *       - ESP_OK: Success
  *       - ESP_FAIL: Failure