perf bench: Fix memcpy/memset output

perf bench: Fix memcpy/memset output

The memcpy and memset benchmarks return bogus results when iterations >
0 because the iterations value is not taken into account when
calculating the final result:

 $ perf bench mem memset --only-prefault --length 1GB --iterations 1
 # Running 'mem/memset' benchmark:
 # Copying 1GB Bytes ...

       20.798669 GB/Sec (with prefault)
 $ perf bench mem memset --only-prefault --length 1GB --iterations 10
 # Running 'mem/memset' benchmark:
 # Copying 1GB Bytes ...

        2.086576 GB/Sec (with prefault)
 $ perf bench mem memset --only-prefault --length 1GB --iterations 100
 # Running 'mem/memset' benchmark:
 # Copying 1GB Bytes ...

      212.840917 MB/Sec (with prefault)

Fix this.

Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rabin Vincent <rabin@rab.in>
Cc: Rabin Vincent <rabinv@axis.com>
Link: http://lkml.kernel.org/r/1417535441-3965-3-git-send-email-rabin.vincent@axis.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>