The dev_pm_genpd_set_performance_state() could in principle be called for a
device that has a different PM domain type attached than a genpd. This
would lead to a problem as dev_to_genpd() uses the container_of macro.

Address this problem by using dev_to_genpd_safe() instead.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>