Input: fix input_free_device() implementation

input_free_device can't just call kfree because if input_register_device
fails after successfully registering corresponding class device there
is a chance that someone could get a reference to it. We need to use
input_put_device() to make sure that we don't delete input device until
last reference to it was dropped.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>