ring: store memzone pointer

ring: store memzone pointer

Add a new field to the rte_ring structure to store the memzone pointer which
contains the ring. For rings created using rte_ring_create(), the field will
be set automatically.

This new field will allow users of the ring to query the numa node a ring is
allocated on, or to get the physical address of the ring, if so needed.

The rte_ring structure will also maintain ABI compatibility, as the
structure members, after the new one, are set to be cache line aligned,
so leaving a space.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>