perf machine: Introduce machine__kernel_maps()

That returns the a data structure contained the ordered list of kernel
modules + the main kernel maps, one more step in removing the
MAP__{FUNCTION,VARIABLE} split.

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: https://lkml.kernel.org/n/tip-qsgbxfyaohc80c9ma049dubm@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/vmlinux-kallsyms.c

@@ -20,7 +20,7 @@ int test__vmlinux_matches_kallsyms(struct test *test __maybe_unused, int subtest
 	struct map *kallsyms_map, *vmlinux_map, *map;
 	struct machine kallsyms, vmlinux;
 	enum map_type type = MAP__FUNCTION;
-	struct maps *maps = &vmlinux.kmaps.maps[type];
+	struct maps *maps = machine__kernel_maps(&vmlinux);
 	u64 mem_start, mem_end;
 	bool header_printed;
 
@@ -228,7 +228,7 @@ next_pair:
 
 	header_printed = false;
 
-	maps = &kallsyms.kmaps.maps[type];
+	maps = machine__kernel_maps(&kallsyms);
 
 	for (map = maps__first(maps); map; map = map__next(map)) {
 		if (!map->priv) {