rtc: rtc-at91rm9200: remove unnecessary platform_set_drvdata()

The driver core clears the driver data to NULL after device_release or
on probe failure, since commit 0998d063 ("device-core: Ensure drvdata
= NULL when no driver is bound").  Thus, it is not needed to manually
clear the device driver data to NULL.
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-at91rm9200.c

@@ -438,7 +438,6 @@ static int __exit at91_rtc_remove(struct platform_device *pdev)
 
 	rtc_device_unregister(rtc);
 	iounmap(at91_rtc_regs);
-	platform_set_drvdata(pdev, NULL);
 
 	return 0;
 }