perf tools: Convert to LIBUNWIND_SUPPORT

For building perf without libunwind, we can set NO_LIBUNWIND=1 as a
argument of make.  It then defines NO_LIBUNWIND_SUPPORT macro for C code
to do the proper handling.  However it usually used in a negative
semantics - e.g. #ifndef - so we saw double negations which can be
misleading.  Convert it to a positive form to make it more readable.

Also change NO_PERF_REGS macro to HAVE_PERF_REGS for the same reason.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1348824728-14025-5-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>