perf: Use consistent include paths for libbpf

Fix perf to include libbpf header files with the bpf/ prefix, to
be consistent with external users of the library.

Signed-off-by: Toke Høiland-Jørgensen <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Acked-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/perf/examples/bpf/5sec.c

···
    Copyright (C) 2018 Red Hat, Inc., Arnaldo Carvalho de Melo <[e-mail]>
 */
 
-#include <bpf.h>
+#include <bpf/bpf.h>
 
 int probe(hrtimer_nanosleep, rqtp->tv_sec)(void *ctx, int err, long sec)
 {

tools/perf/examples/bpf/empty.c

···
-#include <bpf.h>
+#include <bpf/bpf.h>
 
 license(GPL);

tools/perf/examples/bpf/sys_enter_openat.c

···
  * the return value.
  */
 
-#include <bpf.h>
+#include <bpf/bpf.h>
 
 struct syscall_enter_openat_args {
 	unsigned long long unused;

tools/perf/include/bpf/pid_filter.h

···
 #ifndef _PERF_BPF_PID_FILTER_
 #define _PERF_BPF_PID_FILTER_
 
-#include <bpf.h>
+#include <bpf/bpf.h>
 
 #define pid_filter(name) pid_map(name, bool)
 

tools/perf/include/bpf/stdio.h

···
 // SPDX-License-Identifier: GPL-2.0
 
-#include <bpf.h>
+#include <bpf/bpf.h>
 
 struct bpf_map SEC("maps") __bpf_stdout__ = {
        .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,

tools/perf/include/bpf/unistd.h

···
 // SPDX-License-Identifier: LGPL-2.1
 
-#include <bpf.h>
+#include <bpf/bpf.h>
 
 static int (*bpf_get_current_pid_tgid)(void) = (void *)BPF_FUNC_get_current_pid_tgid;