Before DAMON is merged in the mainline, the concept of 'regions update
interval' has generalized to be used as the time interval for update of
any monitoring operations related data structure, but the document has not
updated properly.  This commit updates the document for better
consistency.

Link: https://lkml.kernel.org/r/20220222170100.17068-4-sj@kernel.orgSigned-off-by: NSeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>