perf hists: Introduce struct perf_hpp_list

perf hists: Introduce struct perf_hpp_list

Gather output and sort lists under struct perf_hpp_list, so we could
have multiple instancies of sort/output format entries.

Replacing current perf_hpp__list and perf_hpp__sort_list lists with
single perf_hpp_list instance.

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/1453109064-1026-15-git-send-email-jolsa@kernel.org
[ Renamed fields to .{fields,sorts} as suggested by Namhyung and acked by Jiri ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>