perf utils: Silence "Couldn't synthesize bpf events" warning for EPERM

Synthesizing BPF events is only supported for root. Silent warning msg
when non-root user runs perf-record.
Reported-by: David Carrillo-Cisneros <davidca@fb.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Tested-by: David Carrillo-Cisneros <davidca@fb.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: kernel-team@fb.com
Link: http://lkml.kernel.org/r/20190204193140.719740-1-songliubraving@fb.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/bpf-event.c

@@ -236,8 +236,8 @@ int perf_event__synthesize_bpf_events(struct perf_tool *tool,
 			pr_debug("%s: can't get next program: %s%s",
 				 __func__, strerror(errno),
 				 errno == EINVAL ? " -- kernel too old?" : "");
-			/* don't report error on old kernel */
-			err = (errno == EINVAL) ? 0 : -1;
+			/* don't report error on old kernel or EPERM  */
+			err = (errno == EINVAL || errno == EPERM) ? 0 : -1;
 			break;
 		}
 		fd = bpf_prog_get_fd_by_id(id);