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>

samples/bpf/sock_example.c

@@ -26,7 +26,8 @@
 #include <linux/if_ether.h>
 #include <linux/ip.h>
 #include <stddef.h>
-#include "libbpf.h"
+#include <bpf/bpf.h>
+#include "bpf_insn.h"
 #include "sock_example.h"
 
 char bpf_log_buf[BPF_LOG_BUF_SIZE];