selftests/bpf: fix inet_csk_accept prototype in test_sk_storage_tracing.c

Recent kernel change ([0]) changed inet_csk_accept() prototype. Adapt
progs/test_sk_storage_tracing.c to take that into account.

  [0] 92ef0fd5 ("net: change proto and proto_ops accept type")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240528223218.3445297-1-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c

@@ -84,7 +84,7 @@ int BPF_PROG(trace_tcp_connect, struct sock *sk)
 }
 
 SEC("fexit/inet_csk_accept")
-int BPF_PROG(inet_csk_accept, struct sock *sk, int flags, int *err, bool kern,
+int BPF_PROG(inet_csk_accept, struct sock *sk, struct proto_accept_arg *arg,
 	     struct sock *accepted_sk)
 {
 	set_task_info(accepted_sk);