rtc: msm6242: Initialize drvdata before registering device

Commit f44f7f9 ("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-msm6242.c

@@ -214,6 +214,7 @@ static int __init msm6242_rtc_probe(struct platform_device *dev)
 		error = -ENOMEM;
 		goto out_free_priv;
 	}
+	platform_set_drvdata(dev, priv);
 
 	rtc = rtc_device_register("rtc-msm6242", &dev->dev, &msm6242_rtc_ops,
 				  THIS_MODULE);
@@ -223,10 +224,10 @@ static int __init msm6242_rtc_probe(struct platform_device *dev)
 	}
 
 	priv->rtc = rtc;
-	platform_set_drvdata(dev, priv);
 	return 0;
 
 out_unmap:
+	platform_set_drvdata(dev, NULL);
 	iounmap(priv->regs);
 out_free_priv:
 	kfree(priv);