cpufreq: tegra124: add missing of_node_put()

of_cpu_device_node_get() will increase the refcount of device_node,
it is necessary to call of_node_put() at the end to release the
refcount.

Fixes: 9eb15dbb ("cpufreq: Add cpufreq driver for Tegra124")
Cc: <stable@vger.kernel.org> # 4.4+
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>