selftests/damon: Add executable permission to test scripts

When running the test for the damon subsystem, there are a lot of
warnings because test scripts do not have executable permission,
for example:

Warning: file debugfs_attrs.sh is not executable
Warning: file debugfs_schemes.sh is not executable
Warning: file debugfs_target_ids.sh is not executable
...

This patch adds executable permission to test scripts to eliminate
these warnings.

Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

selftests/damon: test removed scheme sysfs dir access bug

A DAMON sysfs user could start DAMON with a scheme, remove the sysfs
directory for the scheme, and then ask stats or schemes tried regions
update. The related logic were not aware of the already removed directory
situation, so it was able to results in invalid memory accesses. The fix
has made with commit 8468b486612c ("mm/damon/sysfs-schemes: skip stats
update if the scheme directory is removed"), though. Add a selftest to
prevent such kinds of bugs from being introduced again.

Link: https://lkml.kernel.org/r/20221201170834.62823-1-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>