selftests/bpf: add test_sysctl and map_tests/tests.h to .gitignore

Missing files are:
* tools/testing/selftests/bpf/map_tests/tests.h - autogenerated
* tools/testing/selftests/bpf/test_sysctl - binary

Fixes: 51a0e301 ("bpf: Add BPF_MAP_TYPE_SK_STORAGE test to test_maps")
Fixes: 1f5fa9ab ("selftests/bpf: Test BPF_CGROUP_SYSCTL")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>