perf top: Add poll_idle to the skip list

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20090925220239.GA5488@ghostprotocols.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>