perf machine: Add method for common kernel_map(FUNCTION) operation

And it is also a step in the direction of killing the separation of data
and text maps in map_groups.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-rrds86kb3wx5wk8v38v56gw8@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/map.c

@@ -235,7 +235,7 @@ struct map *map__new2(u64 start, struct dso *dso, enum map_type type)
  */
 bool __map__is_kernel(const struct map *map)
 {
-	return machine__kernel_map(map->groups->machine, map->type) == map;
+	return __machine__kernel_map(map->groups->machine, map->type) == map;
 }
 
 static void map__exit(struct map *map)