cpufreq: Enable COMPILE_TEST on Arm drivers

COMPILE_TEST is useful for build testing without requiring a specific
architecture's compiler. Enable it for most of the Arm CPUFreq drivers.

As Kconfig.arm is only included on ARM and ARM64, COMPILE_TEST is only
enabled for those architectures until that is dropped.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>