perf tools: Include errno.h where needed

Removing it from util.h, part of an effort to disentangle the includes
hell, that makes changes to util.h or something included by it to cause
a complete rebuild of the tools.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-ztrjy52q1rqcchuy3rubfgt2@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/drv_configs.c

@@ -17,6 +17,7 @@
 #include "evlist.h"
 #include "evsel.h"
 #include "pmu.h"
+#include <errno.h>
 
 static int
 perf_evsel__apply_drv_configs(struct perf_evsel *evsel,