perf tools: Fix lsdir to set errno correctly

Fix lsdir() to set correct positive error number (ENOMEM).  Since
"errno" must have a positive error number instead of negative number,
fix lsdir to set it correctly.
Signed-off-by: NMasami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: e1ce726e ("perf tools: Add lsdir() helper to read a directory")
Link: http://lkml.kernel.org/r/20160511135127.23943.40644.stgit@devboxSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/util.c

@@ -139,7 +139,7 @@ struct strlist *lsdir(const char *name,
 
 	list = strlist__new(NULL, NULL);
 	if (!list) {
-		errno = -ENOMEM;
+		errno = ENOMEM;
 		goto out;
 	}