ring: move code in a new header file

ring: move code in a new header file

Move the common part of rte_ring.h into rte_ring_generic.h.
Move the memory barrier part into update_tail().

No functional changes here.

Suggested-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Suggested-by: Konstantin Ananyev <konstantin.ananyev@intel.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: Hemant Agrawal <hemant.agrawal@nxp.com>