Revert "staging: dgap: remove unneeded kfree() in dgap_tty_register_ports()"

This reverts commit 0ade4a34 as it was
wrong.

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>