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>

Documentation/ABI/testing/sysfs-tty

@@ -87,19 +87,22 @@ What:		/sys/class/tty/ttyS<x>/close_delay
 Date:		October 2012
 Contact:	Alan Cox <alan@linux.intel.com>
 Description:
-		 Show the closing delay time for this port in ms.
+		Show the closing delay time for this port in centiseconds.
 
-		 These sysfs values expose the TIOCGSERIAL interface via
-		 sysfs rather than via ioctls.
+		These sysfs values expose the TIOCGSERIAL interface via
+		sysfs rather than via ioctls.
 
 What:		/sys/class/tty/ttyS<x>/closing_wait
 Date:		October 2012
 Contact:	Alan Cox <alan@linux.intel.com>
 Description:
-		 Show the close wait time for this port in ms.
+		Show the close wait time for this port in centiseconds.
 
-		 These sysfs values expose the TIOCGSERIAL interface via
-		 sysfs rather than via ioctls.
+		Waiting forever is represented as 0. If waiting on close is
+		disabled then the value is 65535.
+
+		These sysfs values expose the TIOCGSERIAL interface via
+		sysfs rather than via ioctls.
 
 What:		/sys/class/tty/ttyS<x>/custom_divisor
 Date:		October 2012