mfd: mc13xxx-core: Initialize the lock prior to using it

After request_threaded_irq() is called there is a chance that an interrupt
may occur before the 'mc13xxx->lock' is initialized, which will trigger a kernel
oops.

In order to prevent that, move the initialization of 'mc13xxx->lock' prior to
requesting the interrupts.
Suggested-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Acked-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/mc13xxx-core.c

@@ -660,13 +660,13 @@ int mc13xxx_common_init(struct device *dev)
 	if (ret)
 		return ret;
 
+	mutex_init(&mc13xxx->lock);
+
 	ret = request_threaded_irq(mc13xxx->irq, NULL, mc13xxx_irq_thread,
 			IRQF_ONESHOT | IRQF_TRIGGER_HIGH, "mc13xxx", mc13xxx);
 	if (ret)
 		return ret;
 
-	mutex_init(&mc13xxx->lock);
-
 	if (mc13xxx_probe_flags_dt(mc13xxx) < 0 && pdata)
 		mc13xxx->flags = pdata->flags;