perf kmem: Increase "Hit" column length

It's fairly easy to overflow the "Hit" column with just few
seconds of tracing so increase the column length to avoid broken
formatting.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
LKML-Reference: <1263921803-10214-1-git-send-email-penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>