cpufreq: TEGRA: Set policy->cpus from driver->init()

For multicore SoC's, with cores sharing clock line, we are required to set
policy->cpus and policy->related_cpus with mask of cpus.

With following patch, we need to set policy->cpus with mask of all possible cpus
and policy->related_cpus would be filled automatically by the cpufreq core.

commit 4948b355e90080cd5ec1e91189f65a01e4186ef2
Author: Viresh Kumar <viresh.kumar@linaro.org>
Date:   Tue Jan 29 14:39:08 2013 +0000

    cpufreq: Simplify cpufreq_add_dev()

Current Tegra driver fills only ->related_cpus and not ->cpus, which looks to be
incorrect. Lets fix it.

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