perf, tools: Add support for usr_time and sys_time tool events

BROKEN doesn't work.

Support system time and user time output so that it can be specified
in CSV output.

This is easy to add using the tool event infrastructure.

% perf stat -e sys_time,usr_time,cycles grep -rq foo

 Performance counter stats for 'grep -rq foo':

         2,963,000 ns   sys_time
         2,979,000 ns   usr_time
         6,393,790      cycles

       0.005856066 seconds time elapsed

       0.002979000 seconds user
       0.002963000 seconds sys

Signed-off-by: Andi Kleen <ak@linux.intel.com>