rt2x00: Cleanup rfkill

The label exit_free_polldev is no longer used and can be removed.
input_free_polled_device() also calls input_free_device(), so
don't call it seperatly.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>