soc: qcom: rpmh-rsc: Correctly ignore CPU_CLUSTER_PM notifications

Our switch statement doesn't have entries for CPU_CLUSTER_PM_ENTER,
CPU_CLUSTER_PM_ENTER_FAILED, and CPU_CLUSTER_PM_EXIT and doesn't have
a default.  This means that we'll try to do a flush in those cases but
we won't necessarily be the last CPU down.  That's not so ideal since
our (lack of) locking assumes we're on the last CPU.

Luckily this isn't as big a problem as you'd think since (at least on
the SoC I tested) we don't get these notifications except on full
system suspend.  ...and on full system suspend we get them on the last
CPU down.  That means that the worst problem we hit is flushing twice.
Still, it's good to make it correct.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Fixes: 985427f997 ("soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches")
Reported-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200504104917.v6.1.Ic7096b3b9b7828cdd41cd5469a6dee5eb6abf549@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/soc/qcom/rpmh-rsc.c

@@ -819,6 +819,9 @@ static int rpmh_rsc_cpu_pm_callback(struct notifier_block *nfb,
 	case CPU_PM_EXIT:
 		cpumask_clear_cpu(smp_processor_id(), &drv->cpus_entered_pm);
 		goto exit;
+	default:
+		ret = NOTIFY_DONE;
+		goto exit;
 	}
 
 	ret = rpmh_rsc_ctrlr_is_busy(drv);