perf tools: Move generic barriers out of perf-sys.h

perf tools: Move generic barriers out of perf-sys.h

We will need it for atomic.h, so move it from the ad-hoc tools/perf/
place to a tools/ subset of the kernel arch/ hierarchy.

The parisc stuff was just using the asm-generic/barrier.h, no need to
introduce a tools/arch/parisc/ tree just yet.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-tfas9bs1gje0hfsvhqgrosd6@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>