perf tools: Convert to LIBELF_SUPPORT

For building perf without libelf, we can set NO_LIBELF=1 as a argument
of make.  It then defines NO_LIBELF_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.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1348824728-14025-4-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index fc2f770..dacae4b 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -48,7 +48,7 @@
 	{ "version",	cmd_version,	0 },
 	{ "script",	cmd_script,	0 },
 	{ "sched",	cmd_sched,	0 },
-#ifndef NO_LIBELF_SUPPORT
+#ifdef LIBELF_SUPPORT
 	{ "probe",	cmd_probe,	0 },
 #endif
 	{ "kmem",	cmd_kmem,	0 },