The fix prevents kernel crash caused by twl4030 power button malfunction.

If i2c connection is broken the twl4030 power button driver is unregistered.
The function input_free_device has to be called only when
input_register_device failed. Otherwise input_unregister_device is used.

Signed-off-by: Roman Tereshonkov <roman.tereshonkov@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>