libperf: Avoid counting of nonfilterable fdarray fds

Avoid counting of struct pollfd *entries objects with
fdarray_flag__nonfilterable flag by fdarray__filter().

Nonfilterable objects are still processed if requested revents have been
signaled for them.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/b5ab0d2c-b742-0032-e8d3-c8e2eb423c42@linux.intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>