samples: bpf: include bpf/bpf.h instead of local libbpf.h

There are two files in the tree called libbpf.h which is becoming
problematic.  Most samples don't actually need the local libbpf.h
they simply include it to get to bpf/bpf.h.  Include bpf/bpf.h
directly instead.

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/tracex7_user.c b/samples/bpf/tracex7_user.c
index 8a52ac4..ea6dae7 100644
--- a/samples/bpf/tracex7_user.c
+++ b/samples/bpf/tracex7_user.c
@@ -3,7 +3,7 @@
 #include <stdio.h>
 #include <linux/bpf.h>
 #include <unistd.h>
-#include "libbpf.h"
+#include <bpf/bpf.h>
 #include "bpf_load.h"
 
 int main(int argc, char **argv)