test/rwlock: benchmark on all available cores

Add performance test on all available cores to benchmark
the scaling up performance of rw_lock.

Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org
Suggested-by: Gavin Hu <gavin.hu@arm.com>
Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>