perf hist: Remove the needless callchain.h include from hist.h

Nothing that is provided by callchain.h is used there, just things that
should've be directly included in hist.h, such as rbtree.h and a
map_symbol forward declaration.

Remove it so that we reduce the headers dependency tree.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-zivvqfx93w5zzur7hr7h0nlh@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/hist.h

@@ -2,9 +2,9 @@
 #ifndef __PERF_HIST_H
 #define __PERF_HIST_H
 
+#include <linux/rbtree.h>
 #include <linux/types.h>
 #include <pthread.h>
-#include "callchain.h"
 #include "evsel.h"
 #include "header.h"
 #include "color.h"
@@ -13,6 +13,7 @@
 struct hist_entry;
 struct hist_entry_ops;
 struct addr_location;
+struct map_symbol;
 struct mem_info;
 struct branch_info;
 struct symbol;