perf stat: Leave more room for percentages

Triple digit percentages do not fit otherwise.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-7y40wib8n005io7hjpn1dsrm@git.kernel.org


Signed-off-by: Ingo Molnar <mingo@elte.hu>