mac80211: pid: replace open-coded msecs_to_jiffies

Code directly scaling by HZ and rounding can be more efficiently
and clearly performed with msecs_to_jiffies.
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/rc80211_pid_algo.c

@@ -157,9 +157,7 @@ static void rate_control_pid_sample(struct rc_pid_info *pinfo,
 
 	/* In case nothing happened during the previous control interval, turn
 	 * the sharpening factor on. */
-	period = (HZ * pinfo->sampling_period + 500) / 1000;
-	if (!period)
-		period = 1;
+	period = msecs_to_jiffies(pinfo->sampling_period);
 	if (jiffies - spinfo->last_sample > 2 * period)
 		spinfo->sharp_cnt = pinfo->sharpen_duration;
 
@@ -252,9 +250,7 @@ static void rate_control_pid_tx_status(void *priv, struct ieee80211_supported_ba
 	}
 
 	/* Update PID controller state. */
-	period = (HZ * pinfo->sampling_period + 500) / 1000;
-	if (!period)
-		period = 1;
+	period = msecs_to_jiffies(pinfo->sampling_period);
 	if (time_after(jiffies, spinfo->last_sample + period))
 		rate_control_pid_sample(pinfo, sband, sta, spinfo);
 }