net: thunderx: Fix crash when changing rss with mutliple traffic flows

This fixes a crash when changing rss with multiple traffic flows.

While interface teardown, disable tx queues after all NAPI threads
are done. If done otherwise tx queues might be woken up inside NAPI
if any CQE_TX are processed.

Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: Aleksey Makarov <aleksey.makarov@caviumnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>