watchdog: Fix rio watchdog probe function

watchdog: Fix rio watchdog probe function

[ Upstream commit 03717e3d12b625268848414e39beda25e4515692 ]

After sucessfully registering the misc device the driver iounmaps the
hardware registers and kfree's the device data structure. Ouch !

This was introduced with commit e42311d75 (riowatchdog: Convert to
pure OF driver) and went unnoticed for more than a year :)

Return success instead of dropping into the error cleanup code path.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>