selftests: damon: add access_memory to .gitignore

This binary is missing in the .gitignore and stays as an untracked file.

Link: https://lore.kernel.org/r/20240214-damon_selftest_gitignore-v1-1-f517d0f9f783@gmail.com
Link: https://lkml.kernel.org/r/20240221211148.46522-3-sj@kernel.orgSigned-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Singed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Closes: https://lore.kernel.org/all/AS8P193MB1285C963658008F1B2702AF7E4792@AS8P193MB1285.EURP193.PROD.OUTLOOK.COM/Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/.gitignore

@@ -2,3 +2,4 @@
 huge_count_read_write
 debugfs_target_ids_read_before_terminate_race
 debugfs_target_ids_pid_leak
+access_memory