Revert "cpufreq: governor: Fix negative idle_time when configured with CONFIG_HZ_PERIODIC"

Revert commit 0df35026c6a5 (cpufreq: governor: Fix negative idle_time
when configured with CONFIG_HZ_PERIODIC) that introduced a regression
by causing the ondemand cpufreq governor to misbehave for
CONFIG_TICK_CPU_ACCOUNTING unset (the frequency goes up to the max at
one point and stays there indefinitely).

The revert takes subsequent modifications of the code in question into
account.

Fixes: 0df35026c6a5 (cpufreq: governor: Fix negative idle_time when configured with CONFIG_HZ_PERIODIC)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=115261
Reported-and-tested-by: Timo Valtoaho <timo.valtoaho@gmail.com>
Cc: 4.5+ <stable@vger.kernel.org> # 4.5+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/cpufreq_governor.c

@@ -193,12 +193,8 @@ unsigned int dbs_update(struct cpufreq_policy *policy)
 		wall_time = cur_wall_time - j_cdbs->prev_cpu_wall;
 		j_cdbs->prev_cpu_wall = cur_wall_time;
 
-		if (cur_idle_time <= j_cdbs->prev_cpu_idle) {
-			idle_time = 0;
-		} else {
-			idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
-			j_cdbs->prev_cpu_idle = cur_idle_time;
-		}
+		idle_time = cur_idle_time - j_cdbs->prev_cpu_idle;
+		j_cdbs->prev_cpu_idle = cur_idle_time;
 
 		if (ignore_nice) {
 			u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];