net/bnxt: fix missing barriers in completion handling

net/bnxt: fix missing barriers in completion handling

Ensure that Rx/Tx/Async completion entry fields are accessed
only after the completion's valid flag has been loaded and
verified. This is needed for correct operation on systems that
use relaxed memory consistency models.

Fixes: 2eb53b134aae ("net/bnxt: add initial Rx code")
Fixes: 6eb3cc2294fd ("net/bnxt: add initial Tx code")
Cc: stable@dpdk.org
Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>