cpufreq: Tegra: drop wrapper around tegra_update_cpu_speed()

Tegra has implemented an unnecessary wrapper over tegra_update_cpu_speed(), i.e.
tegra_target(), which wasn't doing anything apart of calling
tegra_update_cpu_speed(). Get rid of that and use tegra_target() directly.

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>