Add a simple test case for ensuring tried_regions directory existence.

Link: https://lkml.kernel.org/r/20221101220328.95765-7-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>