selftests/damon/sysfs: test address range damos filter

selftests/damon/sysfs: test address range damos filter

Add a selftest for checking existence of addr_{start,end} files under
DAMOS filter directory, and 'addr' damos filter type input of DAMON sysfs
interface.

Link: https://lkml.kernel.org/r/20230802214312.110532-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>