bpf: selftest: Remove enum tcp_ca_state from bpf_tcp_helpers.h

The enum tcp_ca_state is available in <linux/tcp.h>.
Remove it from the bpf_tcp_helpers.h to avoid conflict when the bpf prog
needs to include both both <linux/tcp.h> and bpf_tcp_helpers.h.

Modify the bpf_cubic.c and bpf_dctcp.c to use <linux/tcp.h> instead.
The <linux/stddef.h> is needed by <linux/tcp.h>.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200925000452.3859313-1-kafai@fb.com

tools/testing/selftests/bpf/bpf_tcp_helpers.h

@@ -115,14 +115,6 @@ enum tcp_ca_event {
 	CA_EVENT_ECN_IS_CE = 5,
 };
 
-enum tcp_ca_state {
-	TCP_CA_Open = 0,
-	TCP_CA_Disorder = 1,
-	TCP_CA_CWR = 2,
-	TCP_CA_Recovery = 3,
-	TCP_CA_Loss = 4
-};
-
 struct ack_sample {
 	__u32 pkts_acked;
 	__s32 rtt_us;

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

@@ -15,6 +15,8 @@
  */
 
 #include <linux/bpf.h>
+#include <linux/stddef.h>
+#include <linux/tcp.h>
 #include "bpf_tcp_helpers.h"
 
 char _license[] SEC("license") = "GPL";

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

@@ -9,6 +9,8 @@
 #include <stddef.h>
 #include <linux/bpf.h>
 #include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/tcp.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 #include "bpf_tcp_helpers.h"