Add device remove and module exit code to make the driver
functioning as a loadable module.

Fixes: ac289276 (cpufreq: kryo: allow building as a loadable module)
Signed-off-by: Ilia Lin <ilia.lin@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>