net/ena: remove unused offload variables

net/ena: remove unused offload variables

Those variables are being set, but never read. As they seem to be
leftover from the old offloads API and don't have any purpose right
now, they are simply being removed.

Fixes: a4996bd89c42 ("ethdev: new Rx/Tx offloads API")
Cc: stable@dpdk.org
Signed-off-by: Michal Krawczyk <mk@semihalf.com>
Reviewed-by: Artur Rojek <ar@semihalf.com>
Reviewed-by: Dawid Gorecki <dgr@semihalf.com>
Reviewed-by: Igor Chauskin <igorch@semihalf.com>
Reviewed-by: Shai Brandes <shaibran@amazon.com>