PM / devfreq: Show the all available frequencies

The commit a76caf55e5b35 ("thermal: Add devfreq cooling") allows
the devfreq device to use the cooling device. When the cooling down
are required, the devfreq_cooling.c disables the OPP entry with
the dev_pm_opp_disable(). In result, 'available_frequencies'[1]
sysfs node never came to show the all available frequencies.
[1] /sys/class/devfreq/.../available_frequencies

So, this patch uses the 'freq_table' in the 'struct devfreq_dev_profile'
in order to show the all available frequencies.
- If 'freq_table' is NULL, devfreq core initializes them by using OPP values.
- If 'freq_table' is initialized, devfreq core just uses the 'freq_table'.

And this patch adds some comment about the sort way of 'freq_table'.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 997a9eb..1952062 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -84,8 +84,9 @@ struct devfreq_dev_status {
  *			from devfreq_remove_device() call. If the user
  *			has registered devfreq->nb at a notifier-head,
  *			this is the time to unregister it.
- * @freq_table:	Optional list of frequencies to support statistics.
- * @max_state:	The size of freq_table.
+ * @freq_table:		Optional list of frequencies to support statistics
+ *			and freq_table must be generated in ascending order.
+ * @max_state:		The size of freq_table.
  */
 struct devfreq_dev_profile {
 	unsigned long initial_freq;