perf hist: Calculate max_sym name len and nr_entries

Better done when we are adding entries, be it initially of when we're
re-sorting the histograms.

Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol.h

@@ -54,6 +54,7 @@ struct symbol {
 	struct rb_node	rb_node;
 	u64		start;
 	u64		end;
+	u16		namelen;
 	char		name[0];
 };