perf_counter: add more context information

Put in counts to tell which ips belong to what context.

  -----
   | |  hv
   | --
nr | |  kernel
   | --
   | |  user
  -----

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Orig-LKML-Reference: <20090402091319.493101305@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>