cpufreq: tegra: fix implementation of ->exit()

->exit() of drivers should call cpufreq_frequency_table_put_attr() if they have
called cpufreq_frequency_table_get_attr() earlier in init() and they aren't
required to validate their cpufreq table in exit by calling
cpufreq_frequency_table_cpuinfo(). Tegra's driver wasn't calling
cpufreq_frequency_table_put_attr() and was calling
cpufreq_frequency_table_cpuinfo() in exit.

Fix both these issues in it.

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