iio: adc: ti-tsc2046: use us_to_ktime() where appropriate

Given scan_interval_us and time_per_scan_us are both in usecs, it
makes more sense to use us_to_ktime() helper rather than converting
to nanosecs as needed for ns_to_ktime().

Signed-off-by: Xichao Zhao <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/ti-tsc2046.c

···
 		if (priv->poll_cnt < TI_TSC2046_POLL_CNT) {
 			priv->poll_cnt++;
 			hrtimer_start(&priv->trig_timer,
-				      ns_to_ktime(priv->scan_interval_us *
-						  NSEC_PER_USEC),
+				      us_to_ktime(priv->scan_interval_us),
 				      HRTIMER_MODE_REL_SOFT);
 
 			if (priv->poll_cnt >= TI_TSC2046_MIN_POLL_CNT) {
···
 	 * many samples. Reduce the sample rate for default (touchscreen) use
 	 * case.
 	 */
-	tim = ns_to_ktime((priv->scan_interval_us - priv->time_per_scan_us) *
-			  NSEC_PER_USEC);
+	tim = us_to_ktime(priv->scan_interval_us - priv->time_per_scan_us);
 	hrtimer_start(&priv->trig_timer, tim, HRTIMER_MODE_REL_SOFT);
 }