feat(rmt): add API to return the real clock resolution of a channel

Closes https://github.com/espressif/esp-idf/pull/15074

components/esp_driver_rmt/include/esp_private/rmt.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2023-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -28,6 +28,18 @@ extern "C" {
  */
 esp_err_t rmt_get_channel_id(rmt_channel_handle_t channel, int *ret_id);
 
+/**
+ * @brief Get the RMT channel's real clock resolution
+ *
+ * @param[in] channel RMT generic channel that created by `rmt_new_tx_channel()` or `rmt_new_rx_channel()`
+ * @param[out] ret_resolution_hz The real clock resolution in Hz
+ * @return
+ *      - ESP_OK: Get RMT channel resolution successfully
+ *      - ESP_ERR_INVALID_ARG: Get RMT channel resolution failed because of invalid argument
+ *      - ESP_FAIL: Get RMT channel resolution failed because of other reasons
+ */
+esp_err_t rmt_get_channel_resolution(rmt_channel_handle_t channel, uint32_t *ret_resolution_hz);
+
 #ifdef __cplusplus
 }
 #endif