bpf, tls: add tls header to tools infrastructure

Andrey reported a build error for the BPF kselftest suite when compiled on
a machine which does not have tls related header bits installed natively:

  test_sockmap.c:120:23: fatal error: linux/tls.h: No such file or directory
   #include <linux/tls.h>
                         ^
  compilation terminated.

Fix it by adding the header to the tools include infrastructure and add
definitions such as SOL_TLS that could potentially be missing.

Fixes: e9dd904708 ("bpf: add tls support for testing in test_sockmap")
Reported-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/test_sockmap.c

@@ -28,6 +28,7 @@
 #include <linux/sock_diag.h>
 #include <linux/bpf.h>
 #include <linux/if_link.h>
+#include <linux/tls.h>
 #include <assert.h>
 #include <libgen.h>
 
@@ -43,6 +44,13 @@
 int running;
 static void running_handler(int a);
 
+#ifndef TCP_ULP
+# define TCP_ULP 31
+#endif
+#ifndef SOL_TLS
+# define SOL_TLS 282
+#endif
+
 /* randomly selected ports for testing on lo */
 #define S1_PORT 10000
 #define S2_PORT 10001
@@ -114,11 +122,6 @@ static void usage(char *argv[])
 	printf("\n");
 }
 
-#define TCP_ULP 31
-#define TLS_TX 1
-#define TLS_RX 2
-#include <linux/tls.h>
-
 char *sock_to_string(int s)
 {
 	if (s == c1)