timer debug: Hide kernel addresses via %pK in /proc/timer_list

In the continuing effort to avoid kernel addresses leaking to
unprivileged users, this patch switches to %pK for
/proc/timer_list reporting.

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Eugene Teo <eugeneteo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20110212032125.GA23571@outflux.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>