perf sched: Output runtime and context switch totals

After:

-----------------------------------------------------------------------------------
 Task              |  Runtime ms | Switches | Average delay ms | Maximum delay ms |
-----------------------------------------------------------------------------------
 make              |    0.678 ms |       13 | avg:    0.018 ms | max:    0.050 ms |
 gcc               |    0.014 ms |        2 | avg:    0.320 ms | max:    0.627 ms |
 gcc               |    0.000 ms |        2 | avg:    0.185 ms | max:    0.369 ms |
...
-----------------------------------------------------------------------------------
 TOTAL:            |   21.316 ms |       63 |
---------------------------------------------

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>