cpufreq: qcom-hw: Fix probable nested interrupt handling

Re-enabling an interrupt from its own interrupt handler may cause
an interrupt storm, if there is a pending interrupt and because its
handling is disabled due to already done entrance into the handler
above in the stack.

Also, apparently it is improper to lock a mutex in an interrupt contex.

Fixes: 275157b ("cpufreq: qcom-cpufreq-hw: Add dcvs interrupt support")
Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/qcom-cpufreq-hw.c

@@ -335,9 +335,9 @@ static irqreturn_t qcom_lmh_dcvs_handle_irq(int irq, void *data)
 
 	/* Disable interrupt and enable polling */
 	disable_irq_nosync(c_data->throttle_irq);
-	qcom_lmh_dcvs_notify(c_data);
+	schedule_delayed_work(&c_data->throttle_work, 0);
 
-	return 0;
+	return IRQ_HANDLED;
 }
 
 static const struct qcom_cpufreq_soc_data qcom_soc_data = {