cpufreq: tegra: Don't initialize .index field of cpufreq_frequency_table

The Tegra cpufreq driver doesn't use .index field of
cpufreq_frequency_table and so we don't need to initialize it.
Don't initialize it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>