Fix AMD's Data Cache Refills from System event.

After this patch :

 ./tools/perf/perf stat -e l1d -e l1d-misses -e l1d-write -e l1d-prefetch -e l1d-prefetch-miss -e l1i -e l1i-misses -e l1i-prefetch -e l2 -e l2-misses -e l2-write -e dtlb -e dtlb-misses -e itlb -e itlb-misses -e bpu -e bpu-misses ls /dev/ > /dev/null

 Performance counter stats for 'ls /dev/':

        2499484  L1-data-Cache-Load-Referencees             (scaled from 3.97%)
          70347  L1-data-Cache-Load-Misses                  (scaled from 7.30%)
           9360  L1-data-Cache-Store-Referencees            (scaled from 8.64%)
          32804  L1-data-Cache-Prefetch-Referencees         (scaled from 17.72%)
           7693  L1-data-Cache-Prefetch-Misses              (scaled from 22.97%)
        2180945  L1-instruction-Cache-Load-Referencees      (scaled from 28.48%)
          14518  L1-instruction-Cache-Load-Misses           (scaled from 35.00%)
           2405  L1-instruction-Cache-Prefetch-Referencees  (scaled from 34.89%)
          71387  L2-Cache-Load-Referencees                  (scaled from 34.94%)
          18732  L2-Cache-Load-Misses                       (scaled from 34.92%)
          79918  L2-Cache-Store-Referencees                 (scaled from 36.02%)
        1295294  Data-TLB-Cache-Load-Referencees            (scaled from 35.99%)
          30896  Data-TLB-Cache-Load-Misses                 (scaled from 33.36%)
        1222030  Instruction-TLB-Cache-Load-Referencees     (scaled from 29.46%)
            357  Instruction-TLB-Cache-Load-Misses          (scaled from 20.46%)
         530888  Branch-Cache-Load-Referencees              (scaled from 11.48%)
           8638  Branch-Cache-Load-Misses                   (scaled from 5.09%)

    0.011295149  seconds time elapsed.

Earlier it always shows value 0.
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
LKML-Reference: <1245484165.3102.6.camel@localhost.localdomain>
Signed-off-by: NIngo Molnar <mingo@elte.hu>