selftests: bpf: update .gitignore with missing generated files

Update .gitignore with missing generated files.
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/.gitignore

@@ -3,3 +3,10 @@ test_maps
 test_lru_map
 test_lpm_map
 test_tag
+FEATURE-DUMP.libbpf
+fixdep
+test_align
+test_dev_cgroup
+test_progs
+test_verifier_log
+feature