PM / Domains: Fix unsafe iteration over modified list of device links

commit c6e83cac3eda5f7dd32ee1453df2f7abb5c6cd46 upstream.

pm_genpd_remove_subdomain() iterates over domain's master_links list and
removes matching element thus it has to use safe version of list
iteration.

Fixes: f721889f ("PM / Domains: Support for generic I/O PM domains (v8)")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>