samples: bpf: rename libbpf.h to bpf_insn.h

The libbpf.h file in samples is clashing with libbpf's header.
Since it only includes a subset of filter.h instruction helpers
rename it to bpf_insn.h.  Drop the unnecessary include of bpf/bpf.h.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/samples/bpf/test_cgrp2_attach2.c b/samples/bpf/test_cgrp2_attach2.c
index 1af412e..b453e6a 100644
--- a/samples/bpf/test_cgrp2_attach2.c
+++ b/samples/bpf/test_cgrp2_attach2.c
@@ -24,8 +24,9 @@
 #include <unistd.h>
 
 #include <linux/bpf.h>
+#include <bpf/bpf.h>
 
-#include "libbpf.h"
+#include "bpf_insn.h"
 #include "cgroup_helpers.h"
 
 #define FOO		"/foo"