selftests/bpf: Use bpf_tracing_net.h in bpf_cubic

This patch uses bpf_tracing_net.h (i.e. vmlinux.h) in bpf_cubic.
This will allow to retire the bpf_tcp_helpers.h and consolidate
tcp-cc tests to vmlinux.h.
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20240509175026.3423614-7-martin.lau@linux.devSigned-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -14,14 +14,22 @@
  *    "ca->ack_cnt / delta" operation.
  */
 
-#include <linux/bpf.h>
-#include <linux/stddef.h>
-#include <linux/tcp.h>
-#include "bpf_tcp_helpers.h"
+#include "bpf_tracing_net.h"
+#include <bpf/bpf_tracing.h>
 
 char _license[] SEC("license") = "GPL";
 
 #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#define max(a, b) ((a) > (b) ? (a) : (b))
+static bool before(__u32 seq1, __u32 seq2)
+{
+	return (__s32)(seq1-seq2) < 0;
+}
+#define after(seq2, seq1) 	before(seq1, seq2)
+
+extern __u32 tcp_slow_start(struct tcp_sock *tp, __u32 acked) __ksym;
+extern void tcp_cong_avoid_ai(struct tcp_sock *tp, __u32 w, __u32 acked) __ksym;
 
 #define BICTCP_BETA_SCALE    1024	/* Scale factor beta calculation
 					 * max_cwnd = snd_cwnd * beta