perf maps: Add for_each_entry()/_safe() iterators

To reduce boilerplate, provide a more compact form using an idiom
present in other trees of data structures.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-59gmq4kg1r68ou1wknyjl78x@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-event.c

@@ -153,7 +153,7 @@ static struct map *kernel_get_module_map(const char *module)
 		return map__get(pos);
 	}
 
-	for (pos = maps__first(maps); pos; pos = map__next(pos)) {
+	maps__for_each_entry(maps, pos) {
 		/* short_name is "[module]" */
 		if (strncmp(pos->dso->short_name + 1, module,
 			    pos->dso->short_name_len - 2) == 0 &&