net/bnxt: fix Tx hang after port stop/start

net/bnxt: fix Tx hang after port stop/start

Initialize the state of the completion valid indicator
when a completion ring is freed, otherwise completions may
not be processed when a new ring is allocated.

Fixes: 5735eb241947 ("net/bnxt: support Tx batching")
Cc: stable@dpdk.org
Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>