cpufreq: tegra194: Allow building for Tegra234

Support was added for Tegra234 in the referenced commit, but the Kconfig
was not updated to allow building for the arch.

Fixes: 273bc890 ("cpufreq: tegra194: Add support for Tegra234")
Signed-off-by: Aaron Kling <webgeek1234@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>