net/enic: fix crash in secondary process

Both primary and secondary processes may call the queue start/stop,
link update handlers. These functions use the rte_eth_dev pointer
cached in the adapter private data (struct enic). But, this pointer is
valid only in the primary process, as rte_eth_dev addresses may differ
in different processes. Using that cached pointer in secondary
processes leads to a crash.

For the link update handler (enic_link_update), use the rte_eth_dev
pointer passed down from the rte layer as it is valid in the current
process. For the queue start/stop handlers (enic_start_wq and
friends), cache the rte_eth_dev_data pointer in the adapter private
data, and use that. rte_eth_dev_data is in shared memory and its
address is same across processes.

Fixes: 837e68ae94a2 ("net/enic: fix queue stop and start")
Fixes: cf8d9826b7be ("net/enic: extract code for checking link status")
Cc: stable@dpdk.org
Reported-by: Dirk-Holger Lenz <dirk.lenz@ng4t.com>
Signed-off-by: Hyong Youb Kim <hyonkim@cisco.com>
Tested-by: Dirk-Holger Lenz <dirk.lenz@ng4t.com>
Reviewed-by: John Daley <johndale@cisco.com>