cpufreq: tegra194: add online/offline hooks

Implement the light-weight tear down and bring up helpers to reduce the
amount of work to do on CPU offline/online operation.
This change helps to make the hotplugging paths much faster.

Suggested-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Link: https://lore.kernel.org/lkml/20230816033402.3abmugb5goypvllm@vireshk-i7/
[ Viresh: Fixed rebase conflict ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Author: Sumit Gupta

drivers/cpufreq/tegra194-cpufreq.c

@@ -508,6 +508,21 @@ static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
 	return 0;
 }
 
+static int tegra194_cpufreq_online(struct cpufreq_policy *policy)
+{
+	/* We did light-weight tear down earlier, nothing to do here */
+	return 0;
+}
+
+static int tegra194_cpufreq_offline(struct cpufreq_policy *policy)
+{
+	/*
+	 * Preserve policy->driver_data and don't free resources on light-weight
+	 * tear down.
+	 */
+	return 0;
+}
+
 static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy,
 				       unsigned int index)
 {
@@ -535,6 +550,8 @@ static struct cpufreq_driver tegra194_cpufreq_driver = {
 	.target_index = tegra194_cpufreq_set_target,
 	.get = tegra194_get_speed,
 	.init = tegra194_cpufreq_init,
+	.online = tegra194_cpufreq_online,
+	.offline = tegra194_cpufreq_offline,
 	.attr = cpufreq_generic_attr,
 };