hmac: Added Downstream JTAG enable mode for esp32c3

If JTAG is disabled temporarily by burning SOFT_DIS_JTAG, it can be
re-enabled temporarily through esp_hmac_jtag_enable API

components/esp32c3/include/esp_hmac.h

@@ -60,6 +60,35 @@ esp_err_t esp_hmac_calculate(hmac_key_id_t key_id,
         size_t message_len,
         uint8_t *hmac);
 
+/**
+ * @brief Use HMAC peripheral in Downstream mode to re-enable the JTAG, if it is not permanently disabled by HW.
+ *        In downstream mode, HMAC calculations performed by peripheral are used internally and not provided back to user.
+ *
+ * @param key_id Determines which of the 6 key blocks in the efuses should be used for the HMAC calculation.
+ *        The corresponding purpose field of the key block in the efuse must be set to HMAC downstream purpose.
+ *
+ * @param token Pre calculated HMAC value of the 32-byte 0x00 using SHA-256 and the known private HMAC key. The key is already
+ *        programmed to a eFuse key block. The key block number is provided as the first parameter to this function.
+ *
+ * @return
+ *      * ESP_OK, if the calculation was successful,
+ *                if the calculated HMAC value matches with provided token,
+ *                JTAG will be re-enable otherwise JTAG will remain disabled.
+ *                Return value does not indicate the JTAG status.
+ *      * ESP_FAIL, if the hmac calculation failed or JTAG is permanently disabled by EFUSE_HARD_DIS_JTAG eFuse parameter.
+ *      * ESP_ERR_INVALID_ARG, invalid input arguments
+ */
+esp_err_t esp_hmac_jtag_enable(hmac_key_id_t key_id, const uint8_t *token);
+
+/**
+ *  @brief Disable the JTAG which might be enabled using the HMAC downstream mode. This function just clears the result generated
+ *         by calling esp_hmac_jtag_enable() API.
+ *
+ *  @return
+ *       * ESP_OK return ESP_OK after writing the HMAC_SET_INVALIDATE_JTAG_REG with value 1.
+ */
+esp_err_t esp_hmac_jtag_disable(void);
+
 #ifdef __cplusplus
 }
 #endif