net/ring: fix adding MAC addresses

net/ring: fix adding MAC addresses

When .mac_addr_add() was changed to allow a return code, ring was changed
to return -ENOTSUP.  This changes the behavior of the rte_ring driver in
a way that does not maintain backward compatibility.  Additionally, if
the intent is to return -ENOTSUP, you could simply not define the stubs.

Fixes: 6d01e580ac5d ("ethdev: fix adding invalid MAC address")
Cc: stable@dpdk.org
Signed-off-by: Chas Williams <ciwillia@brocade.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>