Docs/ABI/damon: update for DAMOS apply intervals

Update DAMON ABI document for the newly added DAMON sysfs file for DAMOS
apply intervals (apply_interval_us file).

Link: https://lkml.kernel.org/r/20230916020945.47296-10-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/ABI/testing/sysfs-kernel-mm-damon

@@ -151,6 +151,13 @@ Contact:	SeongJae Park <sj@kernel.org>
 Description:	Writing to and reading from this file sets and gets the action
 		of the scheme.
 
+What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/apply_interval_us
+Date:		Sep 2023
+Contact:	SeongJae Park <sj@kernel.org>
+Description:	Writing a value to this file sets the action apply interval of
+		the scheme in microseconds.  Reading this file returns the
+		value.
+
 What:		/sys/kernel/mm/damon/admin/kdamonds/<K>/contexts/<C>/schemes/<S>/access_pattern/sz/min
 Date:		Mar 2022
 Contact:	SeongJae Park <sj@kernel.org>