cpufreq: scpi/scmi: Fix freeing of dynamic OPPs

Since the commit 2a4eb735 "OPP: Don't remove dynamic OPPs from
_dev_pm_opp_remove_table()", dynamically created OPP aren't
automatically removed anymore by dev_pm_opp_cpumask_remove_table(). This
affects the scpi and scmi cpufreq drivers which no longer free OPPs on
failures or on invocations of the policy->exit() callback.

Create a generic OPP helper dev_pm_opp_remove_all_dynamic() which can be
called from these drivers instead of dev_pm_opp_cpumask_remove_table().

In dev_pm_opp_remove_all_dynamic(), we need to make sure that the
opp_list isn't getting accessed simultaneously from other parts of the
OPP core while the helper is freeing dynamic OPPs, i.e. we can't drop
the opp_table->lock while traversing through the OPP list. And to
accomplish that, this patch also creates _opp_kref_release_unlocked()
which can be called from this new helper with the opp_table lock already
held.

Cc: 4.20 <stable@vger.kernel.org> # v4.20
Reported-by: Valentin Schneider <valentin.schneider@arm.com>
Fixes: 2a4eb735 "OPP: Don't remove dynamic OPPs from _dev_pm_opp_remove_table()"
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>