rtc: stm32: use rtc_lock/rtc_unlock

Avoid accessing directly rtc->ops_lock and use the RTC core helpers.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210119220653.677750-14-alexandre.belloni@bootlin.com

drivers/rtc/rtc-stm32.c

@@ -209,7 +209,7 @@ static irqreturn_t stm32_rtc_alarm_irq(int irq, void *dev_id)
 	const struct stm32_rtc_events *evts = &rtc->data->events;
 	unsigned int status, cr;
 
-	mutex_lock(&rtc->rtc_dev->ops_lock);
+	rtc_lock(rtc->rtc_dev);
 
 	status = readl_relaxed(rtc->base + regs->sr);
 	cr = readl_relaxed(rtc->base + regs->cr);
@@ -226,7 +226,7 @@ static irqreturn_t stm32_rtc_alarm_irq(int irq, void *dev_id)
 		stm32_rtc_clear_event_flags(rtc, evts->alra);
 	}
 
-	mutex_unlock(&rtc->rtc_dev->ops_lock);
+	rtc_unlock(rtc->rtc_dev);
 
 	return IRQ_HANDLED;
 }