ring: introduce C11 memory model barrier option

ring: introduce C11 memory model barrier option

This patch is to support C11 memory model barrier in librte_ring.

There are 2 barrier implementation options in librte_ring (suggested
by Jerin).
1. use rte_smp_rmb
2. use load_acquire/store_release(refer to [1]).
The reason why providing 2 options is the performance benchmark
difference in different arm machines, refer to [2].

CONFIG_RTE_RING_USE_C11_MEM_MODEL is provided, and by default it is "n"
on any architectures and only "y" on arm64 so far.

[1] https://github.com/freebsd/freebsd/blob/master/sys/sys/buf_ring.h#L170
[2] http://dpdk.org/ml/archives/dev/2017-October/080861.html

Suggested-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Signed-off-by: Jia He <jia.he@hxt-semitech.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Jianbo Liu <jianbo.liu@arm.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>