perf_counter tools: increase cpu-cycles again

Commit b7368fdd7d decreased the CPU cycles interval 100-fold, but
this is causig kerneltop failures on my Nehalem box:

 aldebaran:/home/mingo/linux/linux/Documentation/perf_counter>
 ./kerneltop
 KernelTop refresh period: 2 seconds
 ERROR: failed to keep up with mmap data

10,000 cycles is way too short.

What we should do instead on mostly-idle systems is some sort of
read/poll timeout, so that we display something every 2 seconds
for sure.

Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>