misc: pti, fix fail paths

Fail paths in ->probe and pti_init are incomplete. Fix that by adding
proper clean-up paths.

Note that we used to leak tty_driver on module unload. This is fixed
here too.

tty_unregister_driver needs not retval checking, so remove that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: J Freyensee <james_p_freyensee@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>