net/ring: fix device pointer on allocation

net/ring: fix device pointer on allocation

When a net_ring device is allocated, its device pointer is not set
before calling rte_eth_dev_probing_finish, which is incorrect.

The following:
  commit 96cb19521147 ("net/ring: use EAL APIs in PMD specific API")
  commit a6992e961050 ("net/ring: set ethernet device field")

already fixed the same issue in 17.08, which was fine at the time.
Adding the hook rte_eth_dev_probing_finish() however created this bug,
as the eth_dev exposed when this hook is executed is expected to be
complete.

Remove the prior attempts to fix the issue in rte_pmd_ring_probe() and
write the pointer properly in do_eth_dev_ring_create().

Fixes: fbe90cdd776c ("ethdev: add probing finish function")
Cc: stable@dpdk.org
Signed-off-by: Gaetan Rivet <grive@u256.net>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>