Replacing perf_evsel arg perf_hpp_fmt's header callback with hists
object.

None of the actual callbacks actually use evsel object, also this will
be helpful in future for non evsel related hist browsers.
Signed-off-by: NJiri 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/1465928361-2442-10-git-send-email-jolsa@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>