docs: ABI: sysfs-tty: close times are in centiseconds

The times for close_delay and closing_wait are in centiseconds, not
milliseconds. Fix the documentation and add details of special values.

Signed-off-by: Simon Arlott <simon@octiron.net>
Link: https://lore.kernel.org/r/30fa035a-709f-58cd-fc1e-fef1367dc6dd@0882a8b5-c6c3-11e9-b005-00805fc181fe.uuid.home.arpa


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>