selftests/damon: add execute permissions to test scripts

Some test scripts are missing executable permissions.  It causes warnings
that make the test output unnecessarily verbose.  Add executable
permissions.

Link: https://lkml.kernel.org/r/20240827030336.7930-4-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Gow <davidgow@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>