Trampoline is not supported in s390.

Fixes: 31123c03 ("selftests/bpf: bpf_setsockopt tests")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220819192155.91713-1-kafai@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>