perf tools: Move everything related to sys_perf_event_open() to perf-sys.h

And remove unneeded include directives from perf-sys.h to prune the
header dependency tree.

Fixup the fallout in places where definitions were being used without
the needed include directives that were being satisfied because they
were in perf-sys.h.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-7b1zvugiwak4ibfa3j6ott7f@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/bench/mem-functions.c

@@ -8,7 +8,7 @@
  */
 
 #include "debug.h"
-#include "../perf.h"
+#include "../perf-sys.h"
 #include <subcmd/parse-options.h>
 #include "../util/header.h"
 #include "../util/cloexec.h"
@@ -20,6 +20,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <sys/time.h>
 #include <errno.h>
 #include <linux/time64.h>