PM: domains: Fix build error for genpd notifiers

The __raw_notifier_call_chain() was recently removed and replaced with
raw_notifier_call_chain_robust(). Recent changes to genpd didn't take that
into account, which causes a build error. Let's fix this by converting to
the raw_notifier_call_chain_robust() in genpd.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Lina Iyer <ilina@codeaurora.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>