selftests/damon: fix selftests by installing drgn related script

selftests/damon: fix selftests by installing drgn related script

drgn_dump_damon_status is not installed during kselftest setup.  It can
break other tests which depend on drgn_dump_damon_status.  Install
drgn_dump_damon_status files to fix broken test.

Link: https://lkml.kernel.org/r/20250812140046.660486-1-ekffu200098@gmail.com
Fixes: f3e8e1e51362 ("selftests/damon: add drgn script for extracting damon status")
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>