cpufreq: tegra20: Allow cpufreq driver to be built as loadable module

Nothing prevents Tegra20 CPUFreq module to be unloaded, hence allow it to
be built as a non-builtin kernel module.
Signed-off-by: NDmitry Osipenko <digetx@gmail.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Acked-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/Kconfig.arm

@@ -264,7 +264,7 @@ config ARM_TANGO_CPUFREQ
 	default y
 
 config ARM_TEGRA20_CPUFREQ
-	bool "Tegra20 CPUFreq support"
+	tristate "Tegra20 CPUFreq support"
 	depends on ARCH_TEGRA
 	default y
 	help