cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING cpufreq driver flag

The policy->transition_latency field is used for multiple purposes
today and its not straight forward at all. This is how it is used:

A. Set the correct transition_latency value.

B. Set it to CPUFREQ_ETERNAL because:
   1. We don't want automatic dynamic switching (with
      ondemand/conservative) to happen at all.
   2. We don't know the transition latency.

This patch handles the B.1. case in a more readable way. A new flag for
the cpufreq drivers is added to disallow use of cpufreq governors which
have dynamic_switching flag set.

All the current cpufreq drivers which are setting transition_latency
unconditionally to CPUFREQ_ETERNAL are updated to use it. They don't
need to set transition_latency anymore.

There shouldn't be any functional change after this patch.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq-nforce2.c

@@ -357,7 +357,6 @@ static int nforce2_cpu_init(struct cpufreq_policy *policy)
 	/* cpuinfo and default policy values */
 	policy->min = policy->cpuinfo.min_freq = min_fsb * fid * 100;
 	policy->max = policy->cpuinfo.max_freq = max_fsb * fid * 100;
-	policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
 
 	return 0;
 }
@@ -369,6 +368,7 @@ static int nforce2_cpu_exit(struct cpufreq_policy *policy)
 
 static struct cpufreq_driver nforce2_driver = {
 	.name = "nforce2",
+	.flags = CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
 	.verify = nforce2_verify,
 	.target = nforce2_target,
 	.get = nforce2_get,