staging: csr: info leak in unifi_cfg_get_info()

"cfg_ap_config" has a number of fields which are not cleared before we
copy them to the user.  I've added a memset() at the beginning to set
everything to zero.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>