selftests/bpf: use ASSERT_MEMEQ to compare bpf flow keys

selftests/bpf: use ASSERT_MEMEQ to compare bpf flow keys

The flow_dissector program currently compares flow keys returned by bpf
program with the expected one thanks to a custom macro using memcmp.

Use the new ASSERT_MEMEQ macro to perform this comparision. This update
also allows to get rid of the unused bpf_test_run_opts variable in
run_tests_skb_less (it was only used by the CHECK macro for its duration
field)

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Link: https://lore.kernel.org/r/20241120-flow_dissector-v3-2-45b46494f937@bootlin.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>