RTC: rtc-omap: Fix a leak of the IRQ during init failure

In omap_rtc_probe error path, free_irq() was using NULL rather than the
driver data as the data pointer so free_irq() wouldn't have matched.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: "George G. Davis" <gdavis@mvista.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: rtc-linux@googlegroups.com
Link: http://lkml.kernel.org/r/%3C1303005778.2889.2.camel%40phoenix%3E
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>