rtc: max8998: Initialize drvdata before registering device

Commit f44f7f96 ("RTC: Initialize kernel state from RTC") uncovered
an issue in a number of RTC drivers, where the drivers call
rtc_device_register before initializing the device or platform drvdata.

This frequently results in null pointer dereferences when the
rtc_device_register immediately makes use of the rtc device, calling
rtc_read_alarm.

The solution is to ensure the drvdata is initialized prior to registering
the rtc device.

CC: Wolfram Sang <w.sang@pengutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: rtc-linux@googlegroups.com
Signed-off-by: John Stultz <john.stultz@linaro.org>

drivers/rtc/rtc-max8998.c

@@ -265,6 +265,8 @@ static int __devinit max8998_rtc_probe(struct platform_device *pdev)
 	info->rtc = max8998->rtc;
 	info->irq = max8998->irq_base + MAX8998_IRQ_ALARM0;
 
+	platform_set_drvdata(pdev, info);
+
 	info->rtc_dev = rtc_device_register("max8998-rtc", &pdev->dev,
 			&max8998_rtc_ops, THIS_MODULE);
 
@@ -274,8 +276,6 @@ static int __devinit max8998_rtc_probe(struct platform_device *pdev)
 		goto out_rtc;
 	}
 
-	platform_set_drvdata(pdev, info);
-
 	ret = request_threaded_irq(info->irq, NULL, max8998_rtc_alarm_irq, 0,
 			"rtc-alarm0", info);
 
@@ -293,6 +293,7 @@ static int __devinit max8998_rtc_probe(struct platform_device *pdev)
 	return 0;
 
 out_rtc:
+	platform_set_drvdata(pdev, NULL);
 	kfree(info);
 	return ret;
 }