cpufreq: rename index as driver_data in cpufreq_frequency_table

The "index" field of struct cpufreq_frequency_table was never an
index and isn't used at all by the cpufreq core.  It only is useful
for cpufreq drivers for their internal purposes.

Many people nowadays blindly set it in ascending order with the
assumption that the core will use it, which is a mistake.

Rename it to "driver_data" as that's what its purpose is. All of its
users are updated accordingly.

[rjw: Changelog]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/cpufreq.h

@@ -410,7 +410,7 @@ extern struct cpufreq_governor cpufreq_gov_conservative;
 #define CPUFREQ_TABLE_END     ~1
 
 struct cpufreq_frequency_table {
-	unsigned int	index;     /* any */
+	unsigned int	driver_data; /* driver specific data, not used by core */
 	unsigned int	frequency; /* kHz - doesn't need to be in ascending
 				    * order */
 };