perf bench numa: Fix typo in options

'R' means access the data via reads instead of writes, fix this typo.

Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1524644707-11030-1-git-send-email-xieyisheng1@huawei.com


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