update .gitignore in selftests/vm

Signed-off-by: Yuan Sun <sunyuan3@huawei.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/vm/.gitignore

@@ -2,3 +2,8 @@ hugepage-mmap
 hugepage-shm
 map_hugetlb
 thuge-gen
+compaction_test
+mlock2-tests
+on-fault-limit
+transhuge-stress
+userfaultfd