spi_slave: add a flag SPI_SLAVE_NO_RETURN_RESULT to bypass return descriptor from ISR

if using this flag, driver willn't return the trans-done descriptor from ISR, so
`spi_slave_get_trans_result()` shouldn't be called.
besides, callback is the only way to know transaction status in that case, so a
`post_trans_cb` will be checked mandatory.

components/driver/include/driver/spi_master.h

@@ -224,6 +224,7 @@ esp_err_t spi_device_queue_trans(spi_device_handle_t handle, spi_transaction_t *
                         out.
  * @return
  *         - ESP_ERR_INVALID_ARG   if parameter is invalid
+ *         - ESP_ERR_NOT_SUPPORTED if flag `SPI_DEVICE_NO_RETURN_RESULT` is set
  *         - ESP_ERR_TIMEOUT       if there was no completed transaction before ticks_to_wait expired
  *         - ESP_OK                on success
  */

components/driver/include/driver/spi_slave.h

@@ -23,7 +23,7 @@ extern "C"
 #define SPI_SLAVE_TXBIT_LSBFIRST          (1<<0)  ///< Transmit command/address/data LSB first instead of the default MSB first
 #define SPI_SLAVE_RXBIT_LSBFIRST          (1<<1)  ///< Receive data LSB first instead of the default MSB first
 #define SPI_SLAVE_BIT_LSBFIRST            (SPI_SLAVE_TXBIT_LSBFIRST|SPI_SLAVE_RXBIT_LSBFIRST) ///< Transmit and receive LSB first
-
+#define SPI_SLAVE_NO_RETURN_RESULT        (1<<2)  ///< Don't return the descriptor to the host on completion (use `post_trans_cb` to notify instead)
 
 typedef struct spi_slave_transaction_t spi_slave_transaction_t;
 typedef void(*slave_transaction_cb_t)(spi_slave_transaction_t *trans);
@@ -158,6 +158,7 @@ esp_err_t spi_slave_queue_trans(spi_host_device_t host, const spi_slave_transact
  *                      out.
  * @return
  *         - ESP_ERR_INVALID_ARG   if parameter is invalid
+ *         - ESP_ERR_NOT_SUPPORTED if flag `SPI_SLAVE_NO_RETURN_RESULT` is set
  *         - ESP_OK                on success
  */
 esp_err_t spi_slave_get_trans_result(spi_host_device_t host, spi_slave_transaction_t **trans_desc, TickType_t ticks_to_wait);