perf bench: Prepare memcpy for merge

The memset benchmark is largely copy-pasted from the memcpy benchmark.
Prepare the memcpy file for merge with memset by extracting out a
generic function.

Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rabin Vincent <rabinv@axis.com>
Link: http://lkml.kernel.org/r/1417535441-3965-1-git-send-email-rabin.vincent@axis.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>