perf hists: Introduce nr_header_lines into struct perf_hpp_list

Currently we support just single line headers, this is first step to
allow more.

Store the number of header lines in perf_hpp_list, which encompasses all
the display/sort entries and is thus suitable to hold this value.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1470583710-1649-2-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
index 4274969..be7a17f 100644
--- a/tools/perf/ui/hist.c
+++ b/tools/perf/ui/hist.c
@@ -441,6 +441,7 @@
 struct perf_hpp_list perf_hpp_list = {
 	.fields	= LIST_HEAD_INIT(perf_hpp_list.fields),
 	.sorts	= LIST_HEAD_INIT(perf_hpp_list.sorts),
+	.nr_header_lines = 1,
 };
 
 #undef HPP__COLOR_PRINT_FNS