ec_commands: add EC_CMD_PWM_GET_FAN_DUTY for getting fan duty cycle

Add host command `EC_CMD_PWM_GET_FAN_DUTY` for host to get current fan
duty cycle setting.

BUG=b:411292427
TEST=make buildall

Change-Id: Ifc51935c807d2a5fe94c03ceef5fb778fdbbef80
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/6466952
Commit-Queue: Sung-Chi Li <lschyi@chromium.org>
Code-Coverage: Zoss <zoss-cl-coverage@prod.google.com>
Reviewed-by: Wai-Hong Tam <waihong@google.com>
Tested-by: Sung-Chi Li <lschyi@chromium.org>

Author: LSChyi

include/ec_commands.h

@@ -2333,6 +2333,16 @@ struct ec_response_pwm_get_duty {
 	uint16_t duty; /* Duty cycle, EC_PWM_MAX_DUTY = 100% */
 } __ec_align2;
 
+#define EC_CMD_PWM_GET_FAN_DUTY 0x0027
+
+struct ec_params_pwm_get_fan_duty {
+	uint8_t fan_idx;
+} __ec_align1;
+
+struct ec_response_pwm_get_fan_duty {
+	uint32_t percent; /* Percentage of duty cycle, ranging from 0 ~ 100 */
+} __ec_align4;
+
 /*****************************************************************************/
 /*
  * Lightbar commands. This looks worse than it is. Since we only use one HOST