perf callchain: Use 'struct map_symbol' in 'struct callchain_cursor_node'

To ease passing around map+symbol, just like done for other parts of the
tree recently.

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

tools/perf/builtin-kmem.c

@@ -412,8 +412,8 @@ static u64 find_callsite(struct evsel *evsel, struct perf_sample *sample)
 				 sizeof(key), callcmp);
 		if (!caller) {
 			/* found */
-			if (node->map)
-				addr = map__unmap_ip(node->map, node->ip);
+			if (node->ms.map)
+				addr = map__unmap_ip(node->ms.map, node->ip);
 			else
 				addr = node->ip;