selftests/bpf: Fix xdp_do_redirect on s390x

selftests/bpf: Fix xdp_do_redirect on s390x

[ Upstream commit 06c1865b0b0c7820ea53af2394dd7aff31100295 ]

s390x cache line size is 256 bytes, so skb_shared_info must be aligned
on a much larger boundary than for x86. This makes the maximum packet
size smaller.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230128000650.1516334-11-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stable-dep-of: 6c20822fada1 ("bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES")
Signed-off-by: Sasha Levin <sashal@kernel.org>