selftests/bpf: Reuse the tcp_sk() from the bpf_tracing_net.h

This patch removes the individual tcp_sk implementations from the
tcp-cc tests. The tcp_sk() implementation from the bpf_tracing_net.h
is reused instead.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20240509175026.3423614-4-martin.lau@linux.dev


Signed-off-by: Alexei Starovoitov <ast@kernel.org>