perf tools: Remove warning()

Now everything uses pr_warning(), so ditch it.

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-hv8r0mgdhk73wtfq3zrhavgx@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/util.h

@@ -17,9 +17,6 @@
 void usage(const char *err) __noreturn;
 void die(const char *err, ...) __noreturn __printf(1, 2);
 int error(const char *err, ...) __printf(1, 2);
-void warning(const char *err, ...) __printf(1, 2);
-
-void set_warning_routine(void (*routine)(const char *err, va_list params));
 
 static inline void *zalloc(size_t size)
 {