perf hists: Introduce hist_entry__filter()

The hist_entry__filter() function is to filter hist entries using sort
key related info.  This is needed to support hierarchy mode since each
hist entry will be associated with a hpp fmt which has a sort key.  So
each entry should compare to only matching type of filters.

To do that, add the ->se_filter callback field to struct sort_entry.
This callback takes 'type' argument which determines whether it's
matching sort key or not.  It returns -1 for non-matching type, 0 for
filtered entry and 1 for not filtered entries.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1456326830-30456-6-git-send-email-namhyung@kernel.org


[ 'socket' is reserved in sys/socket.h, so replace it with 'sk' ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>