rtc: davinci: Initialize drvdata before registering device

Commit f44f7f96a20 ("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: Alessandro Zummo <[e-mail]>
CC: Thomas Gleixner <[e-mail]>
CC: [e-mail]
Signed-off-by: Wolfram Sang <[e-mail]>
[fixed up commit log -jstultz]
Signed-off-by: John Stultz <[e-mail]>

drivers/rtc/rtc-davinci.c

···
 		goto fail2;
 	}
 
+	platform_set_drvdata(pdev, davinci_rtc);
+
 	davinci_rtc->rtc = rtc_device_register(pdev->name, &pdev->dev,
 				    &davinci_rtc_ops, THIS_MODULE);
 	if (IS_ERR(davinci_rtc->rtc)) {
···
 
 	rtcss_write(davinci_rtc, PRTCSS_RTC_CCTRL_CAEN, PRTCSS_RTC_CCTRL);
 
-	platform_set_drvdata(pdev, davinci_rtc);
-
 	device_init_wakeup(&pdev->dev, 0);
 
 	return 0;
···
 fail4:
 	rtc_device_unregister(davinci_rtc->rtc);
 fail3:
+	platform_set_drvdata(pdev, NULL);
 	iounmap(davinci_rtc->base);
 fail2:
 	release_mem_region(davinci_rtc->pbase, davinci_rtc->base_size);