x86: AMD Support for perf_counter

Supported basic performance counter for AMD K7 and later:

$ perfstat -e 0,1,2,3,4,5,-1,-2,-3,-4,-5 ls > /dev/null

 Performance counter stats for 'ls':

      12.298610  task clock ticks     (msecs)

        3298477  CPU cycles           (events)
        1406354  instructions         (events)
         749035  cache references     (events)
          16939  cache misses         (events)
         100589  branches             (events)
          11159  branch misses        (events)
       7.627540  cpu clock ticks      (msecs)
      12.298610  task clock ticks     (msecs)
            500  pagefaults           (events)
              6  context switches     (events)
              3  CPU migrations       (events)

 Wall-clock time elapsed:     8.672290 msecs

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>