test/ring: enhance mp/mc coverage
test/ring: enhance mp/mc coverage

Run ring perf test on all available cores to really verify MPMC operations.
The old way of running on a pair of cores is not enough for MPMC rings.

Suggested-by: Gavin Hu <207ee22c2cf71e20c5b5df8395050c07c07d8709@arm.com>
Signed-off-by: Joyce Kong <c01c57df07e2f34c67ea70652554926ebc164737@arm.com>
Reviewed-by: Ruifeng Wang <a548d51fbc42485a8ba807711a537e88c2b59dd2@arm.com>
Reviewed-by: Honnappa Nagarahalli <01ccf438b971cc1d8919c8a7f18443cae9429d8b@arm.com>
Reviewed-by: Dharmik Thakkar <724f3610823e4b14afc73144686337ac966281c2@arm.com>
Reviewed-by: Ola Liljedahl <6d19e6e0076f8797cfccb58ffb99074265221b72@arm.com>
Reviewed-by: Gavin Hu <207ee22c2cf71e20c5b5df8395050c07c07d8709@arm.com>
Acked-by: Olivier Matz <dfcc1510895413197abb4336e39bb0a3906cba71@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk